ARS NOTES
DEMIL AK PARTS KIT
(updated 10-06-2009)
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Introduction | |
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The first step in building an AK from a parts kit is to disassemble the parts kit, which may have old rivets and receiver pieces remaining. This is the most tedious and important part of the build, as any errors here will make later work much more difficult. The term "Demil" comes from "DeMilitarizing" or turning a military (restricted) part into something that can be sold on the open market. The Romanian AKM-47 rifle, as a machinegun, may not be imported into the US for commercial sales. An importer can "Demilitarize" the rifle in a customs warehouse by torch-cutting the receiver into at least 3 pieces. The result is not a classified as a firearm under US law and can be sold with no restrictions. We must continue the Demil process to reduce the cut rifle to useable components. Demil correctly is an important part of a successful build and likely the most time-consuming task. Improper Demil can create greater difficulties later.
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Demil Barrel & Front Trunion | |
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grind rivet heads off, Go slightly below the level of the receiver, but not all the way through |
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peel one side off. If it doesn't come off easily, you need to cut the rivets deeper. The rear rivet is usually a swell neck and must be ground below flush. |
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peel other side off. Channel lock pliers work well for me, giving plenty of leverage. |
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if you are Demil more than one parts kit at the same time, it is important to scribe the trunion number on the barrel group so they can be correctly rematched later. barrels and trunions are not interchangeable and failure to mark them can cause problems on barrel insertion and headspacing later. |
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80% of barrel pins with drive out with the air hammer. I take 3 separate steps. Trying to drive out with the longest punch will often snap the punch or cause displacement of metal around the head of the pin and prevent it from driving through |
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about 20% of the barrel pins I have encountered will not drive out with the air hammer and must be pressed out. This can be a difficult task as the trunion is not evenly shaped and applying pressure to the pin will cause the trunion to rock. To that end I have devised a fixture for holding the trunions flat. Mine is designed for repeated use, but using my fixture as a guide, you can place shims around the trunion to hold it level |
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Front trunion in fixture |
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Pressing out barrel with AK Builder 1/4" pin adaptor for small ram found on the Harbor Freight 12 ton press. Curtis also makes one for the 20 ton press. The pins are too long and prone to snapping. I cut it in half and only use it as a starter pin, finishing with the air hammer. |
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even broken punches can be reground as "stubbies" for starter punches. I use a power drill to spin the punches against a belt sander for reshaping. Keep quenched to avoid destroying the temper |
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Another simple and effective AK Builder product is the barrel press. It is a bolt with a brass nut, the nut having a relief cut to clear the barrel extractor relief cut. You can also use a solid punch and a copper (pre 1983?) penny to prevent marring the barrel or chamber |
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I typically use a pair of old aluminum vise-jaws to support the front trunion while pressing out the barrel. Make sure you are supporting the trunion and not the rear sight base. I cut my Harbor Freight 12 ton presses apart and welded them back together as smaller, but equally robust bench-top models. |
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AK Builder makes a more sophisticated fixture that clamps around the trunion to support it for barrel removal. While it is a very good unit, I find it slightly faster to simply hold my aluminum blocks together until the barrel is under pressure. |
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barrel with press tension applied |
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barrel driving out. Be sure to catch it so it doesn't hit the ground. |
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After removing the barrel, you must drive out the remainder of the rivets. Do the front ones first so you can clamp the trunion in a vise for removing the rear rivets. Do not squeeze the rear flanges of the front trunion in the vise jaws as they will bend or snap off. |
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note the rear hole is countersunk. You may need to drill the rear rivet out as this countersink makes the rivet grip more tightly, but usually it will come out with the air hammer. Chase the slot the receiver folds into to make sure there are no burrs in it. Even the smallest dent or burr can prevent a smooth joining of the trunion and receiver. |
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This picture shows why some barrel pins are difficult to remove. The phenomena is called "galling" and is when the metal is displaced under high pressure, causing the additional resistance. Most of the time, careful filing of just the galled metal will leave the barrel pin still useable. Just have the galled portion facing up or down during installation, as its the front and back bearing surfaces of the pin that are most important
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Demil Rear Trunion | |
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grind or mill the rivets off the rear trunion in the same manner as the front, going slightly below the level of the receiver. Peel the receiver scrap and the trigger guard of, being careful not to bend the trigger guard. |
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drive out the center portion of the rivets. I use a short, medium, and long punch to reduce punch breakage. This is my stubby "starter" punch |
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On about 20% of the rivets, they will not drive out using the air hammer and must be carefully drilled out. Drill about 1/3 of the length and try the hammer again. If that fails, drill all the way through. Do not elongate (egg-shape) the hole as this will cause erratic rivet expansion and unpredictable rivet head size on assembly. |
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here is my long punch for completing the job |
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chase the slot with a narrow cut-off wheel to remove any burrs. The top bend of the receiver fits into this slit and any burrs or foreign material will prevent the receiver from laying flat against the rear trunion. |
Demil Trigger Guard | |
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trigger guard and magazine catch assembly after removal from rear receiver stub. The hardest part of Demil this section is that it is hard to secure it in a vise - you cannot squeeze too hard without crushing the magazine catch axle pin. A small washer around the protruding portions of the pin may make it easier to grasp in the vise. |
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using a grinding wheel, remove any part of the rivets that is protruding and peel off the small receiver section |
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trigger guard with receiver section removed, leaving the guard with magazine catch assembly and the selector stop plate. |
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It is important that you not oval the holes, or break the selector stop plate. The plate is hardened for wear agains the magazine and as a consequence is a bit brittle. To this end, I like to center drill the holes with the mill before going to the hand drill. It takes a little bit longer, but prevents deforming the holes witha walking drill bit. |
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after centerdrilling, I complete drilling throught the plate with a 5/32" (.1562") drill bit which is just under the 4.00 mm (.1575") hole. You do not need to drill all the way through the rivet, just to the depth of the plate. |
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The plate after drilling out the holes |
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Lift of the plate. If there is any risistance, redrill the holes and rock the bit. Too much pressure prying the plate off can crack it. |
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After removing the plate, punch out the remnants of the rivets. |
Demil Trigger Guard - Updated Technique | |
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This small fixture has made a dramatic improvement in holding the trigger guard to remove the rivets. The specific dimensions are not critical. The purpose if to firmly clamp the trigger guard with the selector stop plate and receiver section si that the rivet heads may be cut off. I used some scrap metal I had on hand. I started with a piece of 3/8" square tubing, but I found that it would deform when I tightened the bolts. So I tried sliding bolts inside but that was problematic. So then I took a 3/8" inner dimension piece of solid square bar stock and hammered it into the square tubing. Then I drilled & tapped it 1/4x20 and bolted a retaining strap. Over time, it started deforming so I added a pair of washers to make it clamp better. The "T" for holding it in the vise is made from 2 small pieces of 3/8" solid square stock, although andy block that can handle tightening in the vise would work. This has cut my Demil time in half over the methods shown in my AK-47 (AKM) build tutorial |
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I have a lot of practice using a heavy angle grinder in a delicate manner. You may be more comfortable with a smaller rotary tool. Here I cut off the rivet heads being careful not to cut into the trigger guard |
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this one I touched the vertical surface - I'll touch it to a scotch-brite wheel after removal to polish out the contact mark. |
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rivet heads removed |
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drilling out the rivet shafts with a 5/32" cobalt drill bit |
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completed. |