How to build an AK type rifle Welcome to the hobby of home building firearms. You are about to embark on a challenge of skill, patience and artistry. When you have finished your build you will have the knowledge and pride that comes from completing a demanding job with your own hands. Here are three of the many home builds I have done: Romanian MD-63 underfolder 7.62x39 Romanian AKM 7.62x39
Polish Tantal 5.45x39
In the past 15 years a number of different firearm "kits" have come onto the market. These are military rifles that have been "de milled" to government specifications for civilian ownership. These "kits" have included the FN FAL series, CETME, HK series and the AK series. Of all of these the AK series is unique in that you, the home builder, can actually make your own receiver without the need for a full machine shop. The AK-47 was designed by Mikhail Kalashnikov during a sick leave from fighting in WW 2. It was adopted by the Red Army in 1949 and has been in service in many different forms ever since. It has been produced in dozens of countries and is available in a variety of configurations. The original round was the 7.62x39 but has been updated to the 5.45x39 for the AK-74. This tutorial is presented in sections for ease of use and understanding. I will cover: Basic tools you will need AK series specific tools Kit selection and 922(r) compliance Choosing a receiver Preparing the parts kit Preparing the receiver Building the receiver (Rivet)
Building the receiver (Screw) Putting a finish on the parts Final assembly of the rifle Please take some time to scan through this tutorial to familiarize yourself with the process and terms used. Getting started CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Tools you will need This list will show the minimum tool selection I believe is necessary to properly complete an AK series rifle build. You may already have some of these tools and I will show you how to make some that are specific to the AK rifle build. Hand tools Minimum 5" bench vise 2lb sledge hammer Set of screw drivers Set of punches Several 3" to 5" "C" clamps 8" vise grip pliers Round, flat and square files Power tools Drill press with vise Dremel tool Angle grinder Jig saw with metal blades 110 volt spot welder or MIG/TIG welder (Optional) The listed tools are used for all types of builds. There are some additional tools that are specific to rivet and screw builds. AK series specific tools Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
AK series specific tools Rivet builds To do a rivet build you will need several tools and jigs to set the rivets. These tools can either be hand set tools or press set tools. You will need the following: Short rivet tool Long rivet tool trigger guard rivet jig Press set tools If you have access to or are buying a shop press there are jigs and tools you can buy or make for setting the rivets. The short rivet tool can be a "Plinker" style jig or a set of modified bolt cutters. If you go with the "Plinker" style jig from AK-Builder it will also do the long rivets. These jigs are available from several suppliers: http://www.ak-builder.com/ak/index.php They have the "Plinker" style jig and the trigger guard jig. http://dpharms.com/ They have the trigger guard jig. http://gunthings.com/ They have the long rivet jig. These are just the suppliers I have done business with and there are many others who supply these items. You can also check the chat boards for tools for sale. Hand set tools To set the rivets by hand you will still need the tools and jigs but you will be able to make them yourself. The short rivets can be set using a modified bolt cutter. I prefer the 36" cutters since they have more metal to work with and they seem to hold up better. You can make these yourself using the angle grinder for around $20.00. They are also available in the
Market section of most AK chat boards. This is what it looks like:
Remove the lower jaw from the cutter and lock it in the bench vise. Use the angle grinder to shape the jaw so the it will fit into the front of the trunnion all the way back to the rear rivet location. Go slowly with the grinding process. You do not want to change the heat treating on the jaw. Take a little off and let cool down and then take some more off. You want to end up with a 1/4" square at the end for setting the rivet. You will also need to make a bucking bar to protect the rivet head and insure that the rivet sets tight.
I made this from a piece of 1/4" scrap. You can make the rivet head detent with the Dremel or a 5/16" ball end mill. To set the long rivets I modified a second set of 36"
bolt cutters.
I did this modification using a 14" chop saw. Once I had them formed I made a rivet head detent in one jaw to form the new rivet head as it was set. I will have more details on how these are used in the "Building the receiver" section. You can also set the long rivets by hand using a bucking plate, a hand punch and a hammer.
Using a piece of 1/4" flat stock you will locate and
mark where the rear rivets go. Make a detent for each rivet head with the Dremel or a 5/16" ball end mill.
Using a piece of 3/8" round bar stock make a detent in one end to form the new rivet head. Clamp the receiver with the trunnion and rivets in place to your bench and use the punch and hammer to set the rivet and form the head. You can use this same process for the center support rivet by reversing the punch and making a flat head for the selector to move over.You can also use the long rivet jig from http://gunthings.com/ in this same fashion. Next up is the trigger guard rivet jig. This jig is used as the bucking bar for riveting the trigger guard on the receiver. Start with the 1/4" x 1 1/2" x 6" piece of steel. Mark a center line length wise and drill a .375" hole 1.750" in from each end. Using the jig
saw with the metal cutting blade make two cuts length wise from hole to hole. You will now have a slot 3" long and approximately .375" wide.
You will now need to finish the slot with files or the Dremel. Square the ends and make the slot only as wide as is needed for a tight fit. The front of the trigger guard is wider than the rest and will also need slight grooves for the mag release rivet to slide through. You can now make the rivet head detents using the Dremel or the 5/16" ball end mill. You can see how the trigger guard will sit in the jig. I will have more details on how these are used in the "Building the receiver" section.
Flat bending jig If you are going to use a bendable flat you will need a bending jig. This is normally used with a shop press but I have seen them used with a hydraulic jack and solid frame. There are several suppliers for the bending jigs: http://www.ak-builder.com/ak/index.php They have several options for this jig. http://dpharms.com/ They offer the basic bending jig. Again, these are only the suppliers I have used. These items are available form other sources or you can check the Market section on the chat boards for used ones for sale. You can also make your own using these plans: http://www.quarterbore.com/images/555thjig_print.pdf Spot welder modification
If you opt to use a spot welder to attach the lower rails you will need to modify the lower tong to fit into the receiver. This can be done with the angle grinder and hammer. You will also need to buy a tap and drill bit to reinstall the tip. Start by removing the lower tong and using the anvil on the bench vise flatten it out to a straight rod.Measure the tong so that it will be the same length as the upper tong when reinstalled. Using the angle grinder flatten out one end as shown and drill and tap it for the tip.Reinstall the tip and shape it as shown in the images.
Barrel press This is an option for reinstalling the barrel if you do not have a shop press. It is very simple to make and works like a charm.All you will need is a 36" piece of 1/4" thread rod, a piece of 1/2" key stock, a 1/4" nut, some thin wall aluminum tubing and a 1/4" tension nut. I bought all of this at ACE hardware.
You will need to make the back locking bar from the 1/2" key stock with the grinder or Dremel. It then needs a 1/4-20 hole drilled and tapped for the draw rod. Screw builds To do a screw build you will need the following tools: Tap Handle 1/4-20 taper tap #7 drill bit 10-32 taper tap #21 drill bits 8-32 taper tap #29 drill bits 6-32 taper tap #36 drill bit Cutting oil Allen wrenches to fit each screw size
I will have more details on how these are used in the "Building the receiver" and assembly sections. Kit selection and 922(r) compliance Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Choosing a receiver You have three basic choices in receivers: 100% finished receiver
These are just what the name implies, 100% finished ready to fit and build. They are available for most common AK rifles and range in price from $50.00 to $100.00 plus. The advantages to this receiver are that you do not have to do any of the build steps. All of the holes and openings are done and the lower rails and center support are installed. In most cases the receiver has been fully heat treated. The down side is the cost. If you are on a budget you can expect to spend an additional $40.00 plus for delivery and FFL transfer. You will want to check the chat boards for reviews of the different 100% receivers to see what issues that other builders may have had. 80% receiver blank
The name is a little misleading. This is basically a piece of 4130 sheet steel bent into the shape of an AK receiver and will usually come with a bondable template to do the finishing. Again, these are available from many sources for around $25.00 to $35.00 plus shipping. The advantages to this type of receiver are that you can have it delivered directly to your home since it is not considered a firearm and the cost. The downside is that you will need a little skill and know-how to finish it as well as some extra tools. It is best to order these from a supplier that can also include the lower rails. Bendable flat
That is just what this is, a flat piece of 4130 sheet steel that has had the holes and openings laser cut and the dimples stamped in. Again they can be purchased from many sources for $13.00 on up and
usually come with the lower rails. The advantages are that all of the "Hard" work has been done and the cost. The downside is that you will need access to a bending jig and press to properly form the receiver. Bending jigs are available for around $150.00 on up or can be rented through some chat boards. If you plan to make several receivers of this type it may be cost effective to buy a bending jig and then sell it once your finished. You can usually recoup most of your investment this way. Last but not least you will need rivets or screws and a center support to do the assembly. For a rivet build you can order a rivet set from http://www.ak-builder.com/ak/index.php or check the chat boards for group buys or individuals selling the sets. You will also need a retainer for the FCG pins. You can use the Shepard's hook wire that came with the kit, one of the retainer plates or a pair of 3/16" "E" clips. For a screw build you will need: 6 10-32 x 1/4" button head cap screws 4 1/4-20 x 3/8" button head cap screws 7 8-32 3/8" button head cap screws 5 8-32 hex nuts 8 6-32 1/4" button head cap screws 2" of 1/4" thick wall OD tubing or 1/4" solid rod for the center support These can be bought from most hardware stores. Preparing the parts kit Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Preparing the parts kit When you receive your parts kit it will look something like this:
Removing the furniture It will be necessary to remove the receiver stubs and old rivets as well as press the barrel out. You will want to start by removing the furniture. On the right side of the rear sight block is a lever that needs to be rotated back and up to release the gas tube. Once it is in the open position you can lift the gas tube up and back to remove it.
Next you will remove the handguard. At the front of the handguard is the retainer. There is a lever on the right inside that needs to be rotated forward 180 degrees. Once this is done you can move the retainer forward and pull the handguard down from the front and off.
Next you will remove the buttstock from the rear trunnion. Start by removing the 2 screws from the top. Once they are out lock the trunnion in the bench
vise and use a ram to tap the buttstock out.
Removing the barrel pin The next step is to remove the barrel pin. In most cases this can be done by locking the front trunnion in the vise and using a punch to tap it out. You can also use a shop press and barrel pin punch adapter. Hammer and punch You want to start with a punch that is larger than the pin to get it to move. It will require several solid blows with the hammer to do this. It is best to hold the punch with the vise grips to avoid damage to your hand. Once the pin has started to move you will finish tapping it out with a .250" punch.
Shop press Install the pin punch adapter to the ram on the press. Place the trunnion on a piece of hard wood (Oak works well) with a 3/8" hole through it. Center the pin over the hole and and start pressing it out with the short pin. Once it starts to move use the longer pin to finish pressing it out.
Pressing out the barrel Next you will press the barrel out of the front trunnion. There are several ways to do this depending on what tools you have access to: Gear puller You can buy a gear puller from most auto parts stores for less that $20. You may need to modify the front arms to fit over the trunnion. Once the trunnion is located in the puller lock it in the vise. I use the "C" clamp to keep the puller stable. Using a piece of 5/8" copper or brass rod as a buffer press the barrel out with a ratchet wrench.
Shop press Place supports on either side of the front trunnion. Using a soft metal (Copper or brass) rod about 5/8" diameter or a steel rod with pennies or nickels as a buffer press the barrel out.
Removing the old receiver stubs and rivets Now you will need to remove the receive stubs from the trunnions. Lock each trunnion in turn into the vise and using the angle grinder remove the rivet heads. Do this to both sides of the trunnions. With the heads removed you can peel off the receiver stubs with the vise grips. Rear trunnion
Front trunnion
To remove the rivets from the front trunnion set it on it's side on the anvil of the bench vise and using a small punch knock the rivets out.
To remove the rivets from the rear trunnion you will need to drill them through. First you will want to center punch the rivets on one side to help the drill bit start. Lock the rear trunnion in the vise on your drill press, being sure that it is level, and drill all the way through the rivet with a .120" bit. Go very slowly, 1/4" at a time and use a lot of cutting oil.
To remove the rivets from the trunnion support it on the jaws of the bench vise and using 1/8" punch
drive the rivets out.
To remove the rivets from the trigger guard you will start by locking it into the bench vise. Use the angle grinder to remove the rivet backs from the inside. Be sure not to damage the selector stop on the spacer plate. Once the rivets have been ground down use the vise grips to pull off the old receiver section.
Next lock the trigger guard into the drill vise and drill through with the .120" bit. Once they have been drilled they can be knocked out.
Removing the gas piston If you are going to use a US made gas piston you will need to remove the original one. In most cases they are held in place by a rivet. You can locate the rivet on either side of the bolt carrier about 1/2" back from the front. It may be necessary to use
sandpaper to see the rivet outline. Place the bolt carrier on it's side on the slightly open jaws of the bench vise and use a center punch to start the rivet out. Use the vise grips to finish the removal. Once the rivet is out you can unscrew the piston from the carrier.
The de mill is now complete and you should have this:
Preparing the receiver Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Preparing the receiver If you have opted for a 100% complete receiver select either RIVET or SCREW build. Bent blank with template Whether your blank came with the template bonded on or you did it yourself you will want to measure all
of the hole placements to ensure accuracy.
The correct hole placement is very important and I highly recommend that you check and remark any holes that are not perfect. To measure the placement go from the top of the rail to the center of the hole being sure to add the thickness of the receiver to the total. The correct measurements are as follows: Safety selector .550" Trigger pin 1.380" Hammer pin 1.100" Center support .750" If your receiver is .040" thick you would add that to each measurement for the correct placement. Once you have all of the holes center punched you can drill them out. Drill the holes from each side, do not try to drill through as this may cause misalignment. Hole diameters: Right side Left side Selector large .375" .200" Selector small .200" None Trigger .200" .276"
Hammer .276" Center support .200"
.200" .200"
You will need to drill the holes and cut the openings. To do this without damaging the blank you will need a mandrel. Cut a piece of wood 1.25" wide and 2" tall about 6" long. You will need to remove 1/2" wide by 1/4" deep section from both sides of the mandrel for proper fit.
Next insert the mandrel into the blank and use a center punch to mark each hole to ensure that the drill bit will not "Walk" off the mark. Drill the holes from each side. Do not try to drill straight through. The bit may "Wander" off center in the mandrel.
Once all of the holes are drilled you will need to cut out the larger openings with the Dremel or a mill. Be
sure to make the cuts undersized and finish them with a file to ensure proper fit.
When all of the holes and cutouts are finished remove the template and you should have something that looks like this:
Go down to heat treating Bendable flat The first step is to lock the flat into the alignment bars of the jig. The flat will have two holes on the
center line at each end. These will line up with the centering pins on the jig. The jig will also have a cutout to fit the mag well detent.
Tighten the bolts in series from the center out to ensure that the flat is held evenly. Use plenty of grease on the sides that will go down the inside of the frame. Place the flat on the bending frame with the bolts down and press the assembly into the frame. Use a 1" block between the jig and the press ram.
Start pumping the press and the receiver will start to form.
If you are using the jig from AK-Builder with the top rail attachment follow the directions you received with it. To form the top rails with all other jigs you will place the full assembly on your work bench and using a hammer start to tap the rails over. Do this slowly. Tap them over the a little at a time for the full length of the receiver.
Once you have them about 90% done use a piece of square bar stock as an anvil to finish. If you do the whole process with the hammer it will still work but will not look as good.
Reverse the jig and press the form out. Wipe off the excess grease.
Secure the receiver sides with a "C" clamp and remove the bottom bar. You will want to check the mag well edges and the left side trigger pin hole. Due to how close they are to the bend line they do not always set flat. A LIGHTtapping with the hammer will finish the forming.
Remove the receiver from the jig taking out the side screws. Lift out the center bar and then the side plates.
You should now have something that looks like this:
Heat treating (If you are doing a screw build please refer to that section for more information) To ensure a long life and proper function you will need to heat treat some spots on the receiver as well as the ejector. This can be easily done with a MAPP gas torch and a pail of water. BE VARY CAREFUL DURING THIS PROCESS! You will want to use gloves and probably move outside. Heat treating the ejector Holding the left lower rail in a pair of pliers heat ejector area to 1500 degrees as shown (Glowing yellow/orange) and then plunge it into the pail of water. Using a fine grain sand paper polish the treated area and re heat to 750 degrees as shown (Dull blue/gray). Let it air cool.
Heat treating the FCG holes The FCG holes are the ones that the trigger and hammer pins go through. Each hole needs to be hardened and then annealed. To harden the holes heat each one to 1500 degrees as shown (Glowing yellow/orange) and then plunge it into the pail of water.
Do this with each of the four holes. Using a fine grain sand paper polish the treated areas to bare metal. Re heat all 4 holes to 750 degrees as shown (Dull blue/gray) and let them air cool.
Rivet build Screw build Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Rivet build It is best to do the build from the front back. This will ensure proper fit and placement of the parts and allow for adjustment of the mag well if needed. Front trunnion Insert the trunnion into the front of the receiver. It may be necessary to trim the top rails to get a proper fit. Once the trunnion is in place you will need to check the rivet hole placement. The trunnion must be flush with the front of the receiver.
Depending on the receiver used the trunnion rivet holes may need to be located and drilled. There are several ways to do this. The first option is to use a "Post-it" note. Place the note on one side of the trunnion and use a marker to show the hole location. Insert the trunnion into the receiver and lock it in place with a "C" clamp and drill the rivet holes. You can drill all the way through to do both side a the same time. You can also make a locator jig to find the holes.
You will want to set the mag well rivets first. These are usually "Swell neck" type rivets. You can see the bevel in the trunnion that needs to be recessed for proper fit. You will need to use a taper punch to make the detent in the receiver.
Hand riveting Insert the rivet into the receiver and through the trunnion. Lock it in place using the bucking bar and a "C" clamp.Set up the bolt cutter tool in the vise as shown and move the receiver/trunnion assembly over the jaw as shown. Apply pressure to the tool handle and the rivet will start to set. Check to be sure it crushing straight and then complete the process. Repeat the steps for the other five rivets.
Repeat for the other 4 rivets.
Press riveting This is done using the "Plinker" style jig. Insert the rivet into the receiver and through the trunnion. Position the receiver/trunnion assembly under the ram and set the rivet by pumping the press. Repeat the steps for the other five rivets. +++Post images+++ Fitting the magazine At this point you will want to fit the magazine into the receiver. Make sure that it seats all the way down. If the catch on the back of the magazine does not set flush to the bottom of the receiver you will need to file the back of the mag well to fit.
Trigger guard Place the selector stop/spacer on the bottom of the receiver flush with back of the mag well. Be sure to locate the tab on the right side of the receiver. With the selector stop/spacer in place check the rivet holes. If you needed to file the back of the mag well it may be necessary to adjust the hole placement. This can be done with a round file. If you are using a bent blank you can lock the selector stop/spacer in place with the vise grips and use it as a drilling template. Hand riveting Place the receiver up side down on your work bench and position the selector stop/spacer and the trigger guard. Insert a rivet into each hole. Lower the trigger guard jig over the assembly.
If you are using a jig you bought you can turn it over and secure the receiver to the jig using some scrap wood and a "C" clamp. Set the jig over the open jaws of the bench vise and use a hammer and punch to flatten the rivets.
If you are using a jig you made per the directions listed earlier you will need to turn it over and secure it in the bench vise. Now you will secure the receiver to the jig using scrap wood and "C" clamps. You will also need to place a piece of 3/16" scrap metal under the rear rivet to hold the receiver level while setting the rivets.
Using the flat end of the punch you made start to set the rivets. Go slowly! You do not want to damage the receiver. Start with light strikes until you get a feel for how much force is needed.
Press riveting Place the receiver up side down on your work bench and position the selector stop/spacer and the trigger guard. Insert a rivet into each hole. Lower the trigger guard jig over the assembly.
Turn it over and secure the receiver to the jig using some scrap wood and a "C" clamp. I modified this jig by welding a 1/4" bolt on each side and use a cross bar to hold the receiver firmly in place. Align the pressing plate with the selector stop plate so all 4 rivets will crush evenly. Position the jig under the ram on the press. Set the spacer bar in place and pump the press until set. Repeat for the rear rivet.
The rivet heads should come out undamaged and there should be no gaps between the receiver and trigger guard. You will also want to insert a magazine to ensure that they will lock in place.
Rear trunnion Inset the trunnion into the receiver. It may be necessary to trim the top rails for proper fit. This can be done with the Demel and a file. Position the trunnion in the receiver and check for proper hole alignment.
If the receiver does not have rivet holes in it you can use the old receiver stub for a template to mark the locations. Use a "C" clamp to lock the trunnion in
place and drill through the same as for the front trunnion. The rear trunnion rivets are usually "Swell neck" type rivets and you will need to use a taper punch to make the detent in the receiver.
Hand riveting with the bolt cutter First thing is to attach the trunnion to the buttstock with the screws. This will help stabilize the receiver while setting the rivets. Inset the trunnion into the receiver and install the front rivet. Lock the rivet in place with the bucking bar and a "C" clamp. Set up the bolt cutter in the bench vise as shown. Place the end of the rivet in the detent in the upper jaw and stat to compress. Check too ensure that the rivet is setting straight. Continue to compress the rivet until you have a domed head.
Hand riveting with the punch and hammer First thing is to attach the trunnion to the buttstock with the screws. This will help stabilize the receiver while setting the rivets. Inset the trunnion into the receiver and install both rivets. Clamp the receiver to the bucking plate and your work bench. Using the end of the punch with the detent start to set the rivet. GO SLOWLY! Start with light strikes until you get a feel for how much force is needed to set the rivet and form a domed head. Complete both rivets.
Press riveting This is done using the "Plinker" style jig from AK-Builder or the long rivet jig from Gunthings. Insert the rivet into the receiver and through the trunnion. Position the receiver/trunnion assembly under the ram and set the rivet by pumping the press. Repeat the steps for the other rivet.
Lower rails At this point you will need to install the lower rails. The lower rails stop the bolt from rotating while it moves forward and transitions to the front trunnion. They need to be set to ensure a smooth transition from rail to trunnion. There are several ways to attach the rails to the receiver. Rail caliber modification The right lower rail that comes with most
commercial flats is set up for the 5.45x39mm rifles. The magazines for these rifles are narrower than the ones for the 7.62x39mm cartridge. The tab on the bottom front of the right lower rail is set up to center the narrower 5.45x39mm magazine and will not allow the 7.62x39mm magazines to be properly seated.
To use this in a 7.62x39mm rifle the tab needs to be reduced by half. This can be done before installation with a grinder or after installation with the Dremel or a file. Spot welding With this process you will install one rail at a time. Start with the left rail. Place it inside the receiver and run the center support rivet through it from the right side. Using a 1/4" drill bit as a spacer position the top of the lower rail level with the transition ledge on the front trunnion. Lock the lower rail in place with the vise grips using a piece of scrap metal as a pad on the outside of the receiver to avoid marring the surface.
Make one spot weld at each end of the rail and remove the vise grips. make 3 more spot welds front and back spaced out evenly.
Repeat this process with the right rail adding a spot weld lower down by the hammer pin hole.
Rosette welding To rosette weld the rails you will need to drill 1/8" holes in the receiver at the same locations where spot welds would be. Use a marker to highlight the side of the receiver and score a line 1/2" down from the top rails. You will now need to mark and drill holes through the receiver for the welds.
Once the holes are made start with the left rail. Place it inside the receiver and run the center support rivet through it from the right side. Using a 1/4" drill bit as a spacer position the top of the lower rail level with the transition ledge on the front trunnion. Lock the lower rail in place with the vise grips using a piece of scrap metal as a pad on the outside of the receiver to avoid marring the surface.
From the outside, using a MIG or TIG welder (Arc welders will usually get too hot and damage the receiver.), Fill in each hole until it is just above the level of the receiver side. +++Post images+++ Once it cools you can use the Dremel or a file to smooth the welds out. Center support The center support gives added rigidity to the receiver and stops the hammer from falling forward when field stripping the rifle. It may be necessary to trim the center support to fit.
Hand riveting This can be done with either the Gunthings long rivet jig or the rear trunnion hand rivet plate you made. Insert the rivet from the left side of the receiver and use the flat end of the punch to form the head. GO SLOWLY! Start with light strikes until you get a feel for how much force is needed to set the rivet. The head needs to be flat so the selector will pass over it.
Press riveting This can be done with either the Gunthings long rivet jig or AK-Builder "Plinker" style jig. Insert the rivet from the left side of the receiver and use the flat end of the punch to form the head. Position the assembly under the ram and set the rivet by pumping the press. The head needs to be flat so the selector will pass over it. Trimming the top rails The top rails need to be trimmed so the bolt carrier and bolt will drop in and move freely. This will entail making several cuts in the top rails and filing them down. Starting at the rear trunnion you will need to mark and cut out the bolt carrier slots. Be sure to cut these under size and file to fit!
Once you have it so the bolt carrier will fit into the slots you will need to trim the rails full length. Use
the Dremel with a sanding wheel to do this. Go slowly and check the bolt carrier fit often!
When you have reduced the rails to the point that the bolt carrier can be forced by hand all the way forward finish trimming the rails with a hand file. You want to get to the point where the bolt carrier will move smoothly back and forth just by tilting the receiver. At this point insert the bolt into the carrier and install it into the receiver as far as it will go. If necessary mark the rails on each side for the wide parts of the bolt and use a file to make cutout for the bolt to drop into. You will also check to see if the bolt will pass the ejector on the left lower rail. If it binds you will want to use a file to reduce the ejector so as not to effect the heat treating.
At this point the receiver is complete and should look like this:
Putting a finish on the parts Home
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Screw build Doing a screw build will produce a nice looking and durable rifle if care is taken to properly thread the parts and secure the screws. It is best to do the build from the front back. This will ensure proper fit and placement of the parts and allow for adjustment of the mag well if needed. Front trunnion Insert the trunnion into the front of the receiver. It may be necessary to trim the top rails to get a proper fit. Mark the top rails to show how far back they will need to be trimmed.
You can use the Dremel and files to do the trimming. The receiver sides should set flat against the trunnion sides.
Depending on the receiver used the trunnion rivet holes may need to be located and drilled. There are several ways to do this. The first option is to use a "Post-it" note. Place the note on one side of the trunnion and use a marker to show the hole location. Insert the trunnion into the receiver and lock it in place with a "C" clamp and drill the rivet holes. You can drill all the way through to do both side a the same time.You can also make a locator jig to find the holes.
Once the trunnion has been fitted and the rivet holes drilled in the receiver you will need to re drill the holes in the trunnion using the #21 drill bit. Next lock the trunnion in the bench vise on it's side and tap the 10-32 threads. GO SLOWLY! Use the cutting oil and back the tap out after every turn to clear the channels. Repeat for the other side.
Inset the trunnion into the receiver and using Locktite, tighten the screws. Place a magazine into
the mag well. The mag catch on the back of the magazine should set flush with the bottom of the receiver. It may be necessary to file the back of the mag well for a proper fit. Trigger guard Place the selector stop/spacer on the bottom of the receiver flush with back of the mag well. Be sure to locate the tab on the right side of the receiver. With the selector stop/spacer in place insert a magazine and check the rivet holes. If you had to file the back of the mag well it may be necessary to adjust the hole placement. This can be done with a round file.Starting with the rear screw insert an 8-32 screw through the trigger guard and receiver. Using Locktite, secure the screw from the inside with an 8-32 nut. Now slide the selector stop in place and do the last 4 8-32 screws.
You can use 8-32 nuts on the front of the trigger guard or you can buy one of the tapped screw plates that are available on the chat boards. Once the screws are in place and secure insert a magazine to be sure that it will lock in place.
Rear trunnion Inset the trunnion into the receiver. It may be necessary to trim the top rails for proper fit. This can be done with the Demel and a file. Position the trunnion in the receiver and check for proper hole alignment. If the receiver does not have rivet holes use the post-it note method as with the front trunnion. Lock the trunnion in place with a "C" clamp and drill through the same as for the front trunnion. Once the trunnion has been fitted and the rivet holes drilled in the receiver you will need to re drill the holes in the trunnion using the #7 drill bit.
Do this from each side and only about 1/2" deep. Next lock the trunnion in the bench vise on it's side and tap the 1/4-20 threads. GO SLOWLY! Use the cutting oil and back the tap out after every turn to clear the channels. Repeat for the other side.Insert the trunnion into the receiver and using Locktite, tighten the screws.
Lower rails Rail caliber modification The right lower rail that comes with most commercial flats is set up for the 5.45x39mm rifles. The magazines for these rifles are narrower than the ones for the 7.62x39mm cartridge. The tab on the bottom front of the right lower rail is set up to center the narrower 5.45x39mm magazine and will not allow the 7.62x39mm magazines to be properly seated.
To use this in a 7.62x39mm rifle the tab needs to be reduced by half. This can be done before installation with a grinder or after installation with the Dremel or a file. This method makes use 6-32 button head screws. With this process you will install one rail at a time. Start with the left rail. Place it inside the receiver and run .200" drill bit through it from the right side. Using a 1/4" drill bit as a spacer position the top of the lower rail level with the transition ledge on the front trunnion. Lock the lower rail in place with the vise grips using a piece of scrap metal as a pad on the outside of the receiver to avoid marring the surface. Use a marker to highlight the side of the receiver and score a line 1/2" down from the top of the rails.
You will now need to mark and drill holes through the receiver and rail for the screws to go through. Tap the receiver and rails for 6-32 screws. At this point you will need to heat treat the rail and holes as outlined in Preparing the receiver .
Apply JB Weld to the back of the lower rail and set in place. Insert the screws from the outside and tighten them down. The JB Weld will form a bond between the rails and the receiver and will also fill in the threads of the screws to lock them in place.
Repeat for the right rail. Center support The center support gives added rigidity to the receiver and stops the hammer from falling forward
when field stripping the rifle. Trim the 1/4" OD tubing or rod to 1.17". Drill and tap the ends for the 8-32 screws. Position the center support between the lower rails and start a screw from each side. It will be necessary to use 2 allen wrenches to tighten them. Be sure to use Locktite on both screws.
Trimming the top rails The top rails need to be trimmed so the bolt carrier and bolt will drop in and move freely. This will entail making several cuts in the top rails and filing them down. Starting at the rear trunnion you will need to mark and cut out the bolt carrier slots. Be sure to cut these under size and file to fit!
Once you have it so the bolt carrier will fit into the slots you will need to trim the rails full length. Use the Dremel with a sanding wheel to do this. Go slowly and check the bolt carrier fit often!
When you have reduced the rails to the point that the bolt carrier can be forced by hand all the way forward finish trimming the rails with a hand file. You want to get to the point where the bolt carrier will move smoothly back and forth just by tilting the receiver. At this point insert the bolt into the carrier and install it into the receiver as far as it will go. If necessary mark the rails on each side for the wide parts of the bolt and use a file to make cutout for the bolt to drop into. You will also check to see if the bolt will pass the ejector on the left lower rail. If it binds you will want to use a file to reduce the ejector so as not to effect the heat treating.
At this point the receiver is complete and should look like this:
Putting a finish on the parts Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Putting a finish on the parts For the purposes of this tutorial I am only going to address spray on finishes. I have done Parkerizing and hot bluing but most people do not have the facilities to try these with any amount of success. The three spray on finishes I have used are: Moly Resin from http://www.molyresin.com/ This is a Polish Tantal in Gray/Black Moly Resin.
Dura Coat from http://www.lauerweaponry.com/ This is a metric FAL in Dura Coat Flat Black.
and Dupli-color 500 or 1200 degree with ceramic from any auto parts store. This is a Romanian AKM in Dupli-color 1200 Flat Black.
Each of these finishes has proven to be very durable. The rifles shown above have each had over 500 rounds fired and multiple cleanings without issues. Of the three only the Dura Coat requires a long curing time of up to three weeks. The Moly Resin and Dupli-color are oven cured and the rifle can be assembled and used at once.
Metal preparation Full sandblasting of the parts is nice but is not necessary. I have found that the original parts from the kits have a rough enough surface that the finish will bond properly. The receiver will need to have the surface scored to achieve a long lasting bond. I have found that using a 3M green pad or fine grit sandpaper used in a circular motion works well for this. It is also very important to totally de grease the parts for a good bond of the finish. I use an engine cleaner followed by brake cleaner. I then bake the parts at 250 degrees on news print followed by more engine cleaner. Application Both the Moly Resin and the Dura Coat need an airbrush to apply. The Dupli-color comes in a shaker can. Moly Resin You will need to heat the parts to 150 degrees before applying the spray. This can be done in you kitchen oven on a cookie sheet. Dura Coat Cold application. Dupli-color Cold application. Curing Moly Resin Oven cured at 400 degrees for one hour. Must be wiped down with light weight oil once it has cooled. Dupli-color Oven cured at 400 degrees for one hour. Dura Coat Needs to set up for 72 hours before the parts can be assembled and up to three weeks to be fully
resistant to solvents. Tips on curing I have made some hooks and stands for the parts out of wire coat hangers. These allow me to hang the barrel and receiver from the top rack in the oven and set up the rest of the parts on a cookie sheet on the lower rack. It is very important that the parts do not touch anything while they are in the oven or the finish will not bond. Final assembly of the rifle Home CYA message: This web page is posted for informational and educational use only. Any other use of the information on this website is solely at the user's risk.
Final assembly of the rifle You should now have something that looks like this:
Pressing the barrel in This is the only "mechanical" process in the final assembly. It can be done with a shop press or with
the barrel press I outlined earlier. Shop press Start by cleaning the inside of the front trunnion and the outside of the chamber end of the barrel. Put some high pressure lube on the inside edge of the front trunnion (I use RCBS case lube.) and start the barrel in by hand. Be sure that the barrel is indexed correctly and is straight and level with the top of the receiver.
Use a 5/8" copper or aluminum rod about 8" long to support the receiver through the mag well with the barrel pointing up. Cushion the muzzle with a penny or nickel to protect it and start pumping the press. The barrel will make some popping sounds as it goes in.
As the barrel gets close to being seated you will need to watch through the barrel pin hole to stop at the proper alignment.
Hand barrel press Start by cleaning the inside of the front trunnion and the outside of the chamber end of the barrel. Put some high pressure lube on the inside edge of the front trunnion (I use RCBS case lube.) and start the barrel in by hand. Be sure that the barrel is indexed correctly and is straight and level with the top of the receiver. Using something to pad the receiver, lock it into the bench vise. Install the bolt carrier all the way forward.
Insert the aluminum tube into the muzzle leaving about 1" exposed. Run the thread rod through the aluminum tubing and out the back of the bolt carrier about 1". Run 2 copper washers onto the thread rod and then the tension nut. Thread the key stock block onto the rod at the back of the bolt carrier being sure that the tang on the bolt carrier is in the slot on the block. Lock the block in place with the 1/4" nut.
Hold the rear block in place and run the copper
washers up to the muzzle. The aluminum tube will move back on it's own. Place some grease on the muzzle and between the copper washers. Run the tension nut up to the washers and snug it down. Start to tighten the tension nut. Be sure to hold the rear sight block to stop the index from changing.As the barrel gets close to being seated watch through the barrel pin hole to see when it is properly aligned.
Checking headspace Unless you have a set of headspace gauges I would advise having the headspace checked by a gunsmith. The first thing to do is strip the bolt and clean the bolt face and the chamber. To strip the bolt you will need to remove the main pin and the extractor pin.
Using a small pin punch driver the main pin out from the bottom and remove the firing pin.
Next, using a small screw driver or punch push the extractor pin out while putting pressure on the extractor face. Remove the extractor and spring. The bolt is now stripped.
Now you will want to completely clean the bolt face and the chamber. Use cleaning solvent and a bore brush to ensure that all residue and grime are removed. The two most common gauges are the "GO" and "NO-GO" and are plainly marked for identification. Be sure that you use gauges made by the same manufacturer to ensure accuracy.
Insert the "GO" gauge into the chamber and close the bolt by hand. The locking lug should seat fully to the top left of the trunnion. Repeat the process with the "NO-GO" gauge. When you seat the bolt on the "NO-GO" gauge use finger pressure only. The bolt should not lock up fully. If you use a lot of pressure you may be able to force it to close. If it closes easily on the gauge then the headspace may need to be reset.
Install the barrel pin Reinstall the pin is just the opposite of removing it. Installing a new gas piston If you have opted to use a US made gas piston as a compliance part it will need to be drilled and riveted in place. Screw the gas piston all the way into the bolt carrier and then back it out 1/2 turn. Use a Sharpie to make a mark through the rivet hole. Unscrew the piston and drill a 1/8" hole through it at the mark.
Insert a rivet and hammer it flat on the anvil of the bench vise. Use the Demel to contour the rivet heads on both sides to match the bolt carrier. Installing the furniture Install the pistol grip nut from the inside of the receiver and screw the grip on.
Install the buttstock. It may require some taps with a rubber mallet to seat all the way. Screw the buttstock in place.
Replace the handguard and the gas tube.
Installing the FCG This section will show the proper installation of the FCG and how it works. First lets look at the parts and how they fit into the receiver.
These are the full auto parts that may have come with your kit. They will not be used in this type of build.
Installing the hammer The first step is to install the hammer. Insert the hammer into the Hammer/Trigger spring as shown. Secure the long ends of the spring to the hammer with a twist tie.
Turn the hammer sideways and lower it into the receiver. Turn it again so the wings on the hammer are to the back and insert a axis pin from the left. Run the pin all the way through to the matching hole on the right side of the receiver. Secure the pin on the left with tape.
Installing the trigger and disconector If you are using a captive system assemble as shown.
Drop the assembly into the receiver and insert a axis pin from the left. Run the pin all the way through to the matching hole on the right side of the receiver. Secure the pin on the left with tape.
If you are using a non captive system drop the trigger into the receiver and start the axis pin from the left side but do not put it all the way through. Insert the disconector spring into disconector and lower them onto the trigger. Push the pin the rest of the way through to the matching hole on the right side of the receiver. Secure the pin on the left with tape.
Locking the axis pins There are 3 basic options for locking the axis pins. The Shepard's hook, a retainer plate or "E" clips. Shepard's hook If you received the full auto parts with your kit you should have a long wire with a coil spring on the end. You can use this to make the Shepard's hook by cutting off the spring. The wire then installs over the pins as shown.
Retainer plate The retainer plate hooks over the hammer pin and rotates down onto the trigger pin. It is held in place by the left side selector arm.
"E" clips Place one "E" clip on each pin as shown.
Installing the safety selector Insert the selector from the right side. Make sure that it seats into the matching hole on the left. Rotate the selector forward and down to the selector stop. Remove the twist tie from the hammer and position the spring legs over the rear arms of the trigger.
Holding the trigger back cock the hammer. Be sure that the disconector grabs it and holds it in place. Release the trigger and the hammer should fall forward to the hook on the trigger.
Rotate the safety selector up until the detent is on the top rail. Pull the trigger. The hammer should not release.
If the hammer drops the safety selector will need to have some metal added to the contact arm. Installing the bolt/carrier and recoil spring Insert the bolt into the carrier and drop the assembly into the receiver. Run the bolt/carrier assemble forward to the front trunnion.
Insert the recoil spring into the bolt carrier and lock it into the rear trunnion.
Insert the top cover into the slot in the front sight block and push it down into the slot in the rear trunnion until it locks in place.
FINISHED!!! You should now have something that looks like this.
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