Saturday, May 21, 2011

AKx25 Pistol (Part 1)

Semi-finished product without furniture.
There's a bunch of AK tokarev builds out there.  This is another one.   I have 10,000 rounds of Tokarev surplus and no gun to shoot it in, so I decided to build one.  The biggest hurdle with AK or AR tokarev guns is finding someone who will build and profile a barrel, and most kits out there won't sell the barrel individually.  The second issue is figuring out how and where to get a bolt.  You can either make one from an AK 74 bolt carrier group, or buy one ready-made.  In this case, the ready-made bolt is an Erie Ordnance Depot tokarev bolt.

After that, the rest is pretty easy.  The magwell is from a pps 43 kit that came with four magazines that I got from Sportsmans guide for about $60.  The receiver is a Tapco flat that I bent on my woodvice (that thing is toast after four builds) with two 1.25" steel strips clamped on the flat.  I chopped about 1/3" off the front of the left rail and moved it forward.

Notice how I kept remnants of the old receiver.
 I tried building two different magwells from scratch (an AR-15 type mag catch and and some other ak-type mag-catch made from square tubing) and they both failed, so I ended up using the magwell from a PPS 43.  I was reluctant to chop up a perfectly good pps-43 lower because I was saving it for another project, but fashioning a magwell from scratch was proving to be the most difficult part of this build and so I had to use this.  I simply cut it right off the lower receiver.  I tried to avoid removing parts of the old receiver that were spot-welded on because I needed the extra metal for tapping and screwing.  It's being held on with four 10-32 screws, two of which are shared with the trunnion.

I fucking love hex screws!
If you're wondering why my barrel is so far forward, it's because it was originally supposed to be a locked breech build (a pump-action, tokarev pistol would be awesome, wouldn't it?).  I was hoping to be able to utilize the ak-74 rotating bolt in addition to the EOD bolt, but somewhere I realized it was just easier to hog everything out with an angle grinder and cut through the lugs.  The locked breach wasn't gonna work with PPS-43 magazines, anyways.  Additionally, with my weldless barrel adaption, the barrel pin is holding the barrel in place and there would be no metal on the barrel to pin into if I moved it further back.

7.63 Mauser rounds almost don't feed due to being too short.
The barrel is really ghetto.  It is from a CZ-52 because 1) it's only $25 and 2) I can't find any other 7.62x25 barrels for less than $90 (with an additional cost for custom profiling it).  I chopped off the underside of the CZ-52 barrel so it was flat and the chamber area could be pressed into a sleeve.  Two set screws are inserted upward through the sleeve and into the flat area, red locktited, then the heads of the screws are chopped and ground smooth.  There's also a cross pin under the barrel holding it into the sleeve (I assume that's what that groove would be used for in a CZ-52).  It uses the regular ak barrel pin.  That barrel pin cuts through the sleeve into the top of the barrel.  I had a hell of a time pressing the barrel pin into the trunnion, so that's gotta mean it's in there pretty good.

BUT WAIT, that's not all!  The main sleeve is extended and the rest of the sleeve has it's own sleeve, so they overlap.  The sleeve has set screws that screw into the other sleeve and secure the barrel in place.  They are locktited and ground smooth.  The smaller sleeve is threaded onto the barrel and locktited in place.  Now, back to the chamber sleeve.  It has holes on the side.  The trunnion screws are extra long and screw through the sleeve and act as set screws on the barrel.  There's no way that barrel is going anywhere.

I guess it sounds like overkill, but I didn't want the barrel flying out or anything.  I also JBwelded the entire inside of the sleeves before I finally screwed them in for good, but you shouldn't rely on JBweld for anything as it tends to crack overtime.  It's really just there as filler.  The barrel has held up over onehundred and fifty rounds so far.  If you want to make it a rifle barrel, you could make the smaller sleeve longer so the overall length is 16.25", blind pin and hard silver solder the threads to make it legal length.  But it's still a pistol barrel with pistol barrel accuracy.  I honestly wouldn't feel comfortable putting my hand ahead of where the extension is screwed on.

Without a top cover.
The CZ-52 barrel is deep chambered, so I shaved off some material from the breach.  I didn't measure it, just judged it by sight.  It is in my NON-EXPERT opinion, that most pistol calibers don't need headspace gauges.  As long as it chambers and ejects it should be good enough.  Next I used a sanding drum to carve out a feed ramp directly in the chamber, then polished it with a dremel wirebrush.  The 7.62x25 round is pretty forgiving with how much you can remove, so go crazy.  I haven't had any case ruptures.  For reference, here's what the absolute MAXIMUM looks like for what unsupported case heads in a 7.62x25 barrel looks like.  I've had about a 25% casehead failure rate with this, probably caused by overpressure from bullets that were pushed into the cases.  I need to ream it out more.

This AR barrel in 7.62x25 has a 25% casehead failure rate. Note the amount of exposed case wall.

The rest of the gun uses spare parts - M-72 RPK rear sight block, an american-made pistol trunnion, an M72 recoil spring, and an Romanian top cover.  Out of the first 25 rounds, I had about seven or eight failures to eject (my ejector wasn't moved forward enough, maybe?).  Turns out that I had too much weight and spring tension when I inserted weights into the recoil spring housing.  After removing the weights from the recoil spring housing, the next 25 rounds went smoothly.  I do find it worrisome with how much force the rounds are stripped from the magazine.  Upon ejecting live rounds, I find that some have the bullet pressed in a little.
No bulged cases or casehead failures.  NOTE: Cracked case necks are normal with surplus tokarev rounds.

I don't see any signs of of stress on the receiver, trunnions, or barrel parts after a total of 150 rounds.   You may have noticed on other people's builds that the FCG holes were egging out and the rear trunnion tearing away from the receiver.  I've been told this is due to the bolt carrier group being too light.  However, on weighing both the AK-74 BCG and the EOD bolt, I notice that they weigh about the same.  I think having a recoil buffer helped.  It still needs final finishing and furniture, but is otherwise finished.  I will have video and pictures of the finished product soon.

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