AK47 Build Tutorial

[lelandEOD]

I wrote this for a friend who I recently roped into building his own AK. I figured since I was doing the work, I may as well share it with my Calguns buddies.



The goal of this article is to outline the process I have developed by simple trial and error to build an AK patterned semi-auto rifle from a barrel-less parts kit. I do not claim to be a subject matter expert and certainly have more to learn. Just because I do things one way does not mean that there is no other suitable way of accomplishing the same task. There are almost as many methodologies to building AK's as there are people who build them. I will point out my reasoning behind why I build up the subassemblies in a specific way where appropriate. You are free to agree or disagree as you see fit. Much of my process is dictated by the tools I have available and the mistakes I've made in the past. My goal here is to maybe save you some heartache, or at least mild aggravation with your build.

This article is for reference only. You, the builder, assume all risk when building a firearm and I will not be held liable for any injury or damage caused as a result of incorrect assembly. Always have your homebuilt firearm inspected by a qualified gunsmith prior to firing it.


Before we begin we need to agree upon some basic nomenclature for the parts that make up your AK. For sanity's sake, I am only going to focus on the most common type of kit being built; the Romanian AKM. There are [usually] minor differences between the AK family of rifles and among the various countries of origin. Barring those minor differences, here is a list of the three major sub assemblies on a Romanian AKM:

BARREL ASSEMBLY:

Barrel

Muzzle Device

Front Sight Base
Front sight pin
Muzzle Device retaining plunger and spring
Retaining pins (x2)
Gas Block
retaining pins (x2)

Hand guard retainer

Gas tube, retaining clip and upper hand guard

Lower Hand guard

Rear Sight Base
Leaf spring
rear sight assembly
retaining pin

Cleaning Rod



RECEIVER ASSEMBLY:

Receiver
Receiver lower rails (x2)
Receiver center support
Receiver rivets

Front Trunnion

Rear Trunnion

Buttstock
Buttplate assembly
Sling attachment
Buttstock screws (x2)

Pistol Grip
Pistol grip screw
Pistol grip nut

Trigger

Disconnector
Disconnector spring

Hammer
Hammer spring

Axis Pins (x2)

Fire Selector Lever

Trigger Guard
Magazine release assembly
Selector stop plate

Dust Cover



BOLT CARRIER ASSEMBLY:

Bolt Carrier

Gas Piston

Bolt Carrier Return Spring

Bolt
Extractor
Extractor spring
Extractor pin
Firing pin
Firing pin retaining pin

ETA: I originally had photos of these parts but the 6 photo per post limit on Calguns made it too lengthy.



Building the Receiver

I use a punch set to stamp my fire selector markings on the side of the receiver before I bend it because it's easiest to punch the receiver while it's still flat.

The trick is to get a good bucking bar behind the receiver flat to keep the soft steel from caving in around the punch lettering and looking like crap. This is a trick I learned after I took this photo:



If you don't care about the selector makings you can just as easily skip this step.

Using an AK-Builder receiver flat bending jig is pretty idiot proof. That being said, here are a couple important tips/points. Lay the flat in the correct orientation in the punch and be mindful of the alignment pins in the magwell as they are different between the AK47 and AK74. Tighten the top plate evenly the same way you'd tighten the cylinder head bolts on an engine. Get the suckers nice and tight.



Be sure the releasing bolts on the bottom of the jig are completely backed out prior to pressing the receiver flat. If one of these bolts are in the way you'll make a mess out of the jig and possibly damage it and/or the receiver. This is especially important at an AK build party where you're using other people's tools. Be sure the guy who just bent his flat backed those things back out before you use it!



Press away until you get the punch completely seated in the die.



Once this is done, I remove the punch from the die and take the die/receiver over to my bench. This is the perfect time to stamp your info/serial number onto the receiver (if you want) while it's still in the punch.


I take the top plate off the punch and use a couple C-clamps to hold it against the side of the receiver.

[lelandEOD]

This makes it real easy to keep the punches even as I spell out my favorite greeting to the BATFE.

This is also a good time to take a straight edge/square to check your fore/aft runout along the receiver. Sometimes they just don't come out of the punch completely square and a little light tapping with a mallet will usually straighten them right out.

Once you're ready to remove your newly manufactured firearm from the punch, please don't try to carelessly pry it off. All you have to do is use a soft mallet to tap the rear alignment pin off the receiver then keep tapping it towards the front until it falls off.





At this point, I install the receiver lower rails into the new receiver. You will notice a couple holes on the AK-Builder receiver flat are not completely drilled. They have starter holes that are drilled after you've got the receiver flat bent and the rails welded in. This is why they are not predrilled like the others.



However, before you weld in the rails, the lower magazine stabilizers should be trimmed. If you are comfortable with the process, you can also trim the ejector at this point. If you haven't done this before, I suggest you leave it alone until to can install the bolt/carrier and hand file it to avoid screwing up. If you take too much material off of the ejector your rifle won't properly eject rounds and you will hate life. Here is photo of the trimmed lower rails:



I get it close with an angle grinder. Once they are installed in the completed receiver I test with several magazines and trim as necessary (do this prior parkerizing/paint).

[lelandEOD]

To install the rails with a spot welder I follow the following steps:

Make certain you don't have any bows in the receiver walls before you weld the rails. Use a straight edge to carefully bend out any hourglass shapes in the receiver or bends in the rails before you install the rails.

Scuff all surfaces with a scotchbrite pad and thoroughly degrease with brake cleaner. I don't handle the parts with my bare hands and wear nitrile gloves to keep greasy fingerprints off my parts.

Install the front trunnion using a flat edge to get it perfectly flush against the front edge of the receiver. I use a pair of vise grips to gently hold the trunnion in place and keep it from moving while I weld the rails.



In the past, I have used the fancy rail alignment jig commercially available but have found that the old school drill bit method more reliable and generally easier. Some people say a 1/4” drill bit works well for both rails but I've found that many of my rifles needed a 15/64” bit on one rail and a 1/4” on the other to be perfectly aligned with the lug recesses on the front trunnion. My personal opinion is to worry less about what size bit is used and more about how well the drill bit aligns the rail with the bolt lug recesses on the front trunnion. Use a couple good C-clamps and/or vice grips to hold the rail in place while you weld the rails.

I kind of glossed over this part because I don't have any photos of the actual welding. I'll update this post the next time I'm putting one together.



Once the rails are installed, I like to drill the center support and hammer/trigger holes that have starter holes pre-drilled on the receiver. Use the 5/32” bit on the center support holes. I let the drill bit self center on the starter hole in the drill press. Then use the #16 (.172”) bit on the left side trigger and hammer holes. Again, let the bit self center on the pilot hole provided. Then, I use the 5mm and 7mm reamer to ream the axis pin holes to the appropriate size.

Now, you have a bent receiver with installed rails and correctly drilled holes. (pic coming soon)

Next, install the center support rivet. In order to do this, it's usually best to take a small hand file and get inside the receiver to clean up any residual burrs left by the drilling operation. It makes it easier to get the support installed between the rails too. I use a pair of vice grips to wrestle the support close to the holes and use a small center punch to work the bastard into place.

Then, install the rivet with the flat side on the right.

This is done to allow the selector lever to ride over the rivet.



Place the receiver into the AK-Builder rivet jig and go to town on it. I make sure to get the friction bolt nice and snug when using the pilot pin. Then replace the pilot pin with the dome shaped pin and press away.



I stop when there is just a sliver of space between the pin and the receiver wall. Any more than this any you run the risk of denting the receiver. The other trick is to be sure the bottom of the receiver is not crooked or canted on the jig. There should be equal distance between the receiver and the jig across the bottom. This means you've got a perfectly perpendicular angle on the press. Looking good!

Next, I drill the holes in the receiver for the front and rear trunnion. There are several methods to drilling the trunnion holes. I personally use the AK-Builder trunnion fixture to drill my holes and have found it to be the most reliable method.



Your mileage may vary. Basically, I clamp the trunnion (with receiver installed) onto the trunnion jig.
Then I slide the receiver aft just enough to expose the first rivet hole. Bring the drill bit down into the hole and get it nice and aligned.

[lelandEOD]

Without moving anything, tighten the C-clamp holding the fixture and gently slide the receiver back into place. If anything moved... Correction: if you even THINK anything may have THOUGHT about moving.. do it again.
Once you're set, gently drill through the receiver with light pressure on the press. Be careful not to drill too far or you'll hit the fixture collar. Then repeat the process for the remaining holes.



I use the provided aluminum plate to keep the receiver level. If you are careful, you can even drill both sides of the other four holes on the trunnion to save some time. Just be sure to have the aluminum plate “near” where your drill bit will push through or the receiver will flex away from the trunnion and your hole will be way off.



The rear trunnion holes are done in a similar fashion. They still give me all sorts of grief and are often very hard to get perfectly square. AK-Builder now sells receiver flats with holes pre-drilled and while they are not always completely on the spot, they make a hard job much easier.

Keep in mind you need to countersink the holes for swell neck rivets.




Now you are ready to heat treat the axis pin holes and the ejector tip.

I am not a heat treating expert but the following method has worked well for me. Feel free to deviate as your conscience dictates.

I use a mixture of salt water and dish soap for my quenching solution. Others use used motor oil with good results. I choose not to use oil because a.) I hate the smell of burning oil, b.) oil is flammable and I like my house, c.) oil can be a pain to get out of the nooks and crannies prior to blasting and can ruin parkerizing, and d.) I hate the smell of burning oil.

[lelandEOD]

In a vain effort to minimize warping during the quenching process, I use small C-Clamps and install the front and rear trunnion (temporarily) to provide as much rigidity as possible. This may or may not be necessary, but it's the way I do it. Then, I heat each pin hole with a MAPP torch to a cherry red and immediately quench the receiver in the bucket. Don't try to do all four holes at the same time. Also, don't forget to do the ejector tip too. Once they've all been hardened, you need to temper the brittle steel. Again, there are several methods to doing this and I just went with what sounded like the easiest. I dry off the receiver and clean it up a bit with a scotchbrite pad. Then, using the MAPP torch again, I heat each hole until I can just barely see the color change to that dull grey/blue. Let it cool on it's own and drink a beer.

The next step is to install the trigger guard and selector stop. Rummage through your rivet set and find four regular rivets (not swell necks) and usually the one short rivet (for the rear trigger guard hole). I use the AK-Builder trigger guard rivet jig and make it a habit of sliding the trigger guard as far forward (towards the mag well opening) as it will go. Some will move and others will not. My logic here is that there is often a bit of fore and aft play in the rivet holes and I'd rather have the mag release too tight than too loose when I try to fit the magazines. You can easily trim off a bit of material but it's much harder to put material back on if there's unwanted slop. Some people also think it's difficult to install the trigger guard rivets with the center support installed. Indeed, I did have to file down the rivet contact plate (ref. Fig 1A) just a bit to clear the lower rail near the hammer pin hole, but the AK builder trigger guard bucking bar has that cut out specifically to clear the center support.

Fig 1A






I also install the trigger guard after the heat treating because I really don't want to introduce my mag release mechanism to saltwater.
If my dremel cutoff wheel is handy, I make my selector notches to replicate the originals. My trick is to temporarily install the fire selector lever and run it up and down a few times to leave the trace from the dimple on the lever.

[lelandEOD]

[lelandEOD]

Now, you can take the barrel and put a thin film of assembly lube/axle grease/whatever you have laying around that looks like a lubricant and put a coating on both the barrel and trunnion bore.

This part takes some experience and a good eye and I'm still waiting for someone to show me a better way: I hand fit the trunnion to the barrel using my calibrated eyeball to correctly orient the trunnion to the barrel. Remember we used a level to (hopefully) align the RSB to vertical using the hand guard retainer as our reference point. Now, I use the vertical sides of the RSB and compare how they look to the vertical wings on the trunnion. I don't pay too much attention to the gap between the trunnion ears and the RSB, because I've seen too many that weren't machined square to begin with. Just get it as close as you can. Nothing is permanent until you drill and pin these parts! There will be plenty of time later to obsess over if everything is perfectly straight or not.




Now, using my handy trunnion support tool, I begin pressing the barrel into the trunnion. Hopefully, it will press on smooth with no popping. If it begins to pop, you are in for some fun. I get it close, like this:




Then start using my no-go gauge to tell me when to stop pressing. When my disassembled bolt won't close on a no-go gauge:

[lelandEOD]

...then I check to see if it'll close on a go gauge.

[lelandEOD]

Before I am satisfied, I install the bolt carrier onto the bolt and recheck. This is the clearance I want to see:

NoGo:


Go:


Now, I am ready to drill the barrel pin hole. If you are using a virgin barrel, you use the standard size pin that comes with the kit and a 7mm drill bit. AK-Builder sells the correct bit. Also, I have not had to ream the holes to get a snug fit with the press.



I've had some aggravation with this recently as my puny 1/3hp drill press doesn't have enough power to drill through many of these holes without binding as it heats up. The solution is to buy a manly drill press but I use a level to square up the trunnion to the drill and use copious amounts of cutting oil to minimize the problem. (Pic coming soon as I get a replacement drill bit)

Once the barrel pin hole is drilled, recheck your headspace to confirm nothing moved.

Now you can use your hydraulic press to carefully press on the RSB, gas block (GB) and front sight base (FSB). The nice thing here is that with the trunnion correctly installed on the barrel, I can slip the receiver assembly onto the trunnion to check for the correct fitment of the top cover.



Press on the RSB until you get a good fit on the top cover and check for vertical alignment with the front trunnion. You can also install the lower hand guard to help look for something crooked. Now, I use my calibrated eyeball to get the GB as close to vertical as possible. It may help to clamp the barreled trunnion in a vise and get a good look at it from several angles before you are satisfied it is straight. Then, I use an AR15 armorers wrench to press on the GB.

[lelandEOD]

I hold the gas tube inserted into the RSB (with the lever locked) as I crank on the press until the GB begins to touch. I don't want the gas tube to rattle around, but don't want it so tight I can't easily remove it. Keep pressing until you achieve a good fit.



Then, do the same thing for the FSB.

I usually keep a barrel nut on the muzzle to protect the crown while I mess with the barrel. When it comes time to install the FSB, I get it close to vertical with my calibrated eyeball and use this clocking rod set to verify it is good to go. Then, in the press, I create this precarious mess to get the FSB on correctly. There is surely a better way of doing this... this is just how I do it.




Please note, I use the bit of brass rod to press against the barrel so that I'm not putting pressure on the trunnion. Without the barrel pin installed, it is possible the barrel could slip a little on the trunnion if you press against it. I use a large socket to press on the FSB until it is seated appropriately.

Again, nothing is pinned at this stage. You should be able to look in the barrel pin hole and see nothing moved.



While the front trunnion is still installed on the barrel, this is a good time to locate and cut the groove in the barrel for the hand guard retainer. I use a blade to mark the approximate position:

[lelandEOD]

Then, using a couple files slowly start to cut a groove for the retainer.

[lelandEOD]

As I inch closer, I use a rubber mallet to tap on the lever to leave an impression or discoloration where the lever is hitting metal. This tells me where to remove more material.





Completed front end! Whoo Hoo!!!

[lelandEOD]

Before you remove the front trunnion from the barrel, slip on the receiver to check the top cover clearance and check the bolt/carrier for freedom of movement.

If you're building an AK47 and haven't already filed the ejector down, you will probably find that the bolt jams when you try to slide it forward. Carefully file material off the ejector until you can run the bolt carrier back and forth and not see much deflection as the bolt passes the ejector. It should move back and forth freely without binding.



If there is friction or a jam, carefully inspect it until you can pinpoint the source of the jam. I've had ejectors hitting the bolt or bolt stem causing jams... gas tubes not completely seated causing the carrier causing jams... crooked rails causing the bolt lugs to hit the trunnion recesses. Take your time, figure it out and file as necessary to get everything moving freely.

Now, it's time to remove the trunnion from the barrel so you can rivet it onto the receiver.



Once you press the barrel 1/8” or so, stop and take a small jewelers file the sharp edge of the barrel inside the barrel pin hole. Knocking the sharp edge off the lip will cut down on the chances you'll gall the barrel when you remove it from the trunnion.





Once they are separated, you are ready to rivet the trunnion to the receiver. I use the AK-Builder jig but a lot of guys have been very successful using the modified bolt-cutter jaws available online as a cheap alternative. Just pay attention to which rivets go where as every kit is different. If you look at the trunnion, it will tell you which holes need swell neck rivets and which need straight neck rivets. The swell neck rivets go in the countersunk holes on the trunnion.



Notice in this photo you can see that I did not trim the lower rails or the ejector yet. A few of these photos are from the first rifle I built. Learn from my mistakes!

[lelandEOD]

Once the front trunnion is correctly riveted to the receiver, you can take a few magazines and start test fitting them to check for good lockup. You may need to take a file or dremel tool and carefully trim some material off of either lower rail support and/or the selector lever stop plate to get the magazines to lock in securely, with little to no slop, and to release easily.




Some people prefer to leave the rear trunnion off the receiver until the barrel is properly installed. This makes it easier to press the barrel out if you go too far when installing the barrel and need to back it out a bit to get the correct alignment with your barrel pin hole.

Personally, I install the front and rear trunnion then install the barrel assembly... but I can see it both ways. Go with whatever makes more sense to you.

I use a spritz of degreaser and a few Q-tips to clean up the hole as I get close. A flashlight backlighting the bore also helps me get the alignment just right.

Use your headspace gauges to confirm the pin alignment. If everything looks great, you can reinstall the barrel pin.

NOTE: It is important to make sure when you use your bolt to check headspace that the bolt stem is not hitting the ejector.


If this happens, it is possible for your bolt to give you an erroneous headspace reading. Use a flashlight and check to see if you can see daylight between the ejector and the bolt stem when it is fully locked into the trunnion. This will ensure you are getting accurate headspace readings.

This is your last chance to make sure you are happy with the alignment of the RSB, GB, and FSB. If so, go ahead and drill and pin the components leaving the last pin and plunger assembly on the FSB off until after you've painted/parkerized. If you don't do this, that little bastard can freeze up if you don't get every last bit of parking solution out of that hole. Ask me how I know...

I won't go into the particulars of finishing the AK kit as there are plenty of resources that cover those topics in more detail and with more authority than I can offer.

If you are going straight ghetto, slap some high temp paint on that bad boy and you are done. If you are wanting a more professional finish you'll need a blast cabinet and either some sort of gun coating like Duracoat or parkerizing equipment.

I parkerize my kits with Manganese phosphate before assembling the barrel to the trunnion only because my ghetto parkerizing tank is too small for a barreled action. They come out with a nice grey/black finish.



Once the parking/painting is done, it's time to assemble the internals and FSB plunger assembly and function test the rifle.



BUT WAIT! There's MORE!

My last step on a virgin barrel build is to drill the gas port. On four of the rifles pictured, I have not drilled the ports so they are single shots (so don't get upset at the lack of bullet buttons). I'm waiting for another solartac group buy!

For me, this is the last step before configuring it to be legal (i.e. BB or grip wrap, pin folding stock) and a test fire.










Since the photos and text make it all a little confusing, here is a summary of the steps I take to build a complete virgin barrel barrel rifle from a kit.

1. Demil the kit you are planning to use:
Drill out rivets from front and rear trunnions
Drill out rivets from trigger guard
Sort out and toss the full auto FCG parts as they are just not good to have around
Press off barrel components, if necessary from barrel stubs

2. Match trunnion size to new barrel (look for matching number stampings)

3. Stamp fire control markings onto the side of the receiver if desired: see this link for examples

4. Bend receiver flat in hydraulic press

5. Stamp manufacturers info to receiver while it's still in the punch (if desired)

6. Trim lower receiver rails

7. Temporarily install the front trunnion and align with receiver edge. Clamp in place

8. Use drill bits to align lower rails and clamp in place. Ensure the rails are level with the bolt lug recesses as viewed through the trunnion bore

9. Once satisfied weld in place using your preferred method

10. Once it's cooled, leave the front trunnion in and slip in the rear trunnion and take the receiver to your drill press to drill/bore the receiver holes. This helps the receiver resist flexing in as you drill.

11. NOTE: Start with the smallest bit (this limits the amount of damage you can do if you bore the wrong hole with the wrong bit).

12. Working from small to large, drill the center support holes with the 5/32” drill bit

13. Next, drill the right side hammer and trigger pin holes with the #16 (.172” bit)

14. Then ream the right side axis pin holes with a 5mm reamer.

15. Flip the receiver over and ream the left side axis pin holes with a 7mm reamer.

16. NOTE: I've always just let the receiver “center” itself in the drill press when drilling these holes and have never had a problem with crooked holes.

17. Deburr the insides of the receiver with a file

18. Install the center support rivet with the flat head on the right side of the receiver and use a rivet jig to crush the rivet

19. Drill front and rear trunnion holes, if they were not already punched into your receiver flat.

20. Clamp the trunnions to the receiver to add some reinforcement and countersink the swell rivet holes

21. Leave the trunnions in the receiver and heat treat the four axis pin holes and the ejector tip

22. Install the trigger guard and selector stop

23. NOTE: if there is any play in the trigger guard rivet holes try to slide the mag release mechanism towards the front of the receiver as you begin to crush them. This creates the tightest configuration possible for your mag fit and may keep you from having a sloppy mag fit.

24. If desired, install the selector lever and use a dremel wheel to cut the selector markings along the arc of travel

25. If you are building from a kit that has already had a complete barrel headspaced to the trunnion you can skip down to #41

26. If you need to populate and install a virgin barrel follow these steps:

27. Check for proper interference fit between the trunnion and barrel

28. Slip fit the RSB, hand guard retainer and GB onto the barrel

29. Orient the RSB to the barrel using the hand guard retainer

30. Install front trunnion onto barrel and use headspace gauges to find proper location

31. Check and double check this!

32. Once satisfied, drill the 7mm barrel pin hole. By doing this before anything else, you will be certain that if anything accidentally moves on you, that your headspace alignment was already set.

33. Press on RSB. When it gets close to the rear edge of the trunnion, take your receiver and slip it on to the trunnion. With the rear trunnion installed (not riveted yet), check your top cover fit.

34. Press on gas block

35. Use gas tube to find a good snug fit that doesn't rattle but doesn't get too tight

36. Install the FSB

37. With the trunnion still installed on the barrel assembly, install the lower hand guard and cut the groove for the hand guard retainer, if your barrel doesn't already have this done.

38. This is a good time to test the fit of your bolt carrier assembly in the receiver. Just slip the receiver onto the barreled trunnion and install the gas tube. You may find you need to trim the ejector on the left rail to get the bolt/carrier to slide past it easily.

39. [/B]Before calling it good, recheck your headspace to make sure nothing moved.[/B]

40. Press off the front trunnion from the barrel taking care not to gall the metal as you press it out.


41. Install and rivet the front trunnion to the receiver.

42. Check magazine fit with several varieties of magazines, if possible

43. Use a dremel to remove a much material as needed from the lower rails and/or selector stop to get good mag lock-up

44. Press barrel assembly onto receiver and confirm headspace again!!!

45. Press in barrel pin

46. Install rear trunnion rivets

47. Verify the RSB, GB, and FSB are all perfectly vertical with no cant. Drill and install pins

48. Drill gas port in barrel using the gas block as a guide

49. Install FCG

50. Install furniture, bullet button, etc. being mindful of the requirements to comply with 922r and CA laws


I think that's it... did I forget anything???

[bigboy]

nice tutorial...