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.243 win based on AK innards

4K views 39 replies 6 participants last post by  TRX 
#1 ·
I drew up some plans for a rifle back in march and have been slowly collecting material and various parts as time/funds permit.




I'm starting with a TAPCO flat and the front end off an M70AB2. Originally, I was going to custom make the entire trunnion, but I thin I can modify the milled stub off the M70 easily to avoid a complete scratch build on the front trunnion.

I decided to go with G3 mags for the 243 shells. The reasoning behind this was the simple fact that I think they are cool as hell looking for a mag. :) The gas block/forward sight and muzzle attachement are also going to look a lot like a G3/HK, so they'll compliment each other.

I'm still undecided on the BCG. I'll probably just modify the M70 BCG. I might have to redo the upper half of the carrier to fit my low-profile needs, but doing that and redoing the piston shouldn't be too hard. Due to a longer gas tube, i was already going to have to redo the piston.

Forward grips will be made from 6061-T6 aluminum and freefloat around the barrel assembly. The barrel is a Rem mod-700 in 243 win. I cut it down to 17.5" and the muzzle is target crowned and outside threaded for 9/16"x24 (i already had those tap/die combo).

I finished my AK bending jig and got it tweaked so it bends the flats to an inside width of 1.245". To use the G3 mags, I'm going with a magwell. I bent up one using 0.032", 1050 steel. This is nice in that it fits just inside the AK frame when properly sized to fit the mags and when the dimples have been flattened. In the pic, it's still a bit large. It'll get the top 1/2" or so trimmed off and fit up into the frame higher than what you see here. I won't trim it until I get the trunnion made and mounted and the rails welded in. It took three tries to get the "perfect" magwell....I don't want to trim too much and screw it up!

I'll get to work on it next weekend...assuming my wife doesn't go into labor this week! ....even then, I still might get to work a bit. :)

Here's pics of the magwell fitting:



 
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#27 ·
well this is getting interesting. do you have a boring bar/ head for the mill??? thats what I would thought to use for the barrel hole. damm wish I had a furnace that would be what I need to do my 50 bmg project.

I hope this all works out for you if you pull it off you will likely be the first home builder I have seen make his own trunion. If you can get a look at a saiga 308 trunion and bolt in regards to the lugs being wider. If you need pics I can likely send you some. If your going to make it, make it stronger than whats already out there.
 
#28 ·
My bolt lugs will only be about 0.020" wider in radius and the same length, but there will be three of them. The shoulders in the trunnion are beefier than the M70 and my MAK90 as well.

One of the drawbacks of the minimill is the lack of horsepower. I really need the next size up for doing these bigger holes and using the larger bits. If we actually sell out old house this Fall, I'll be getting a good general purpose one for myself. It'll be nice to have my own equipment and not have to beg borrow and steal!

I picked up my electric furnaces at surplus auctions for the Universities around here. I paid $40 for the one in the pic...and I got five or six old film projectors, a bag of assorted other crap and an overhead projector that came with it on the pallet. :) Texas A&M changed their auction format. Now they use the online stuff that runs continuous. Much harder to find a deal. Being in Houston now I'll have to see what U of H and the various teaching hospitals use for their surplus sales. Ought to be lots of lab furnaces from the hospitals.

For metalwork, just make sure you get a muffled furnace. Ceramic kilns often have exposed elements. Those are way to easy to break elements in!
 
#29 ·
I have a 1" cobalt end mill and deming bits from 5/8-1". The lathe owner said "no problem" to my idea. It was nice to hear an affirmative response! His only concern was non-symmetry throwing the chuck out of balance. Once I showed him the actual dimensions he didn't think it would be a problem at all. I guess when i said "hunk of 4130" he envisioned a 4 x 6 hunk or similar! :)

I started on the rear trunnion tonight. This is being made from 1.25" square mild steel. I'm making a custom folding stock for it. I really like the looks of the FAL para stocks, but being a stingy bastard I can't bring myself to fork over that much for a stock...just to cut and mod it! I think it will actually be kinda of fun making one. Stocks are always something I'm needing, and I never see "exactly" what I want in one. It'll be nice to finally have what I want. I think I have a pretty good idea for the locking mechanism on it as well, but I'll wait until it's done before I show it :wink:.


Some of the cuts in the trunnion seem to be strictly for tool clearance. I noticed when using a 1/4" endmill, I need to cut an angle on some edges to get the tooling where it needs to be for final cuts and these angles all coincide with where the angled cuts are in the original. That and rounded and angled cuts just make it look more "refined and graceful" (if you can actually use graceful and AK in the same sentence!) as opposed to just a cut up block of steel.
 
#32 ·
A few difficulties, but everything is fine and mom and baby doing great! It came out a pretty good scratch build...loads and ejects just fine now. :) Tends to be kind of squeaky, though.

Brendan Albrecht
6lb 9oz
9/23/09


Of course, might as well take advantage of the down time during delivery....
I snapped this pic and figured all the gun-build forums would like it. I was designing stock parts and such in the delivery room. I had over 8 hrs to spend before it got busy.

 
#33 ·
Here's some barrel work on the 243 (and couple break-action rifles in 357 max and 270 also). For the 243, a section was de-tapered where the gas block will be; the muzzle recessed, crowned at 12* and threaded 9/16-24; the chamber turned down to 0.957 so it will be a nice friction fit for a 0.954 hole.






Here's the rear trunnion base. There will be another part that fits onto the top. I haven't made up my mind what it will look like, so I just did the bottom section. This will get a hinge and a pair of locking-pin holes for the folding stock I'm making.



 
#35 ·
This is a cool thread. I am new to building but i had no idea you could rechamber an AK! I am going to have to check in on this one. How did you resize the bolt face? A .243 has a base dia. of .473 as compared to .445 of the 7.62x39?

you can cut the bolt face on a mill or drill press with the correct end mill or you can do it on a lathe. doing the bolt face is the easy part.
 
#37 ·
There's lots of threads around here for modifying AK's for other calibers. I use a small lathe for facing bolts, chambers, etc. A mill bit works well. I also make use of the steady rest mounted on a section that has been trued to the bore, then use a sharp carbide bit or the mill bit. For this particular one, I'm not modifying existing AK parts, I'm making them from scratch since it required a lot of mods and I wasn't sure I could do what i wanted to do with existing parts. It's a lot more work, but it'll be strong enough for any 243 load and have all the custom features I wanted.

I got some more done on the front trunnion, but have been out of the country for a bit and haven't had a chance to mess much with it. I should have the trunnion done by the end of this week. After that, the bolt will be made, then the bolt carrier and gas system parts. Or at least that's the plan. :) Of course, I just got back yesterday and an coming down with some sort of flu like crud. Who knows what sombody coughed up on me during all the plane and train rides the last couple weeks!:sick:
 
#38 ·
Erie Ordnance Depot does some simplified trunnions for blowback conversions. I've attached a picture. Note that it's welded up from pieces.

Also, there are a lot of weird bumps and cuts on a standard carrier that don't appear to do anything. I suspect they're to accomodate the full-auto bits we don't use.

You could use the same basic idea and use a piece of thickwall tubing to hold the cam track. I first realized that the depth of the track didn't have to be consistent, as long as the bolt lug had enough clearance. You could make some centers for the mill table and "peck" with a center-cutting end mill to make the track, then finish it with a Dremel.

I have three bolt carriers here, and the cam tracks are slightly different in each one. I don't think it matters a whole lot. Also note the important side of the track is the one that unlocks the bolt; the "kicker" on the bullet guide takes care of locking.

One of the carriers I have is from a well-used Maadi, and the track is beaten up a bit. Case hardening or 4130/4140 might be a good idea.

Anyway, I don't think you *have* to use a fancy 4-axis setup to cut the track, at least for DIY purposes. And I'd probably try plain chicken-wire-grade 1018 for the main bits and see how the rail bearing area held up in service. 1018 would be a whole lot cheaper and easier to machine, enough to be worth a try, anyway.
 

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#39 ·
they have had these CARRIERS/BOLTS out for a while now. I have some thing simular in the works woth out the pison for a gude rod build.

as far as making a carrier from scratch for a gas op gun beside the benifit of I made it myself your looking at a lot of work to make a part that can be bought for $20.

Id like to see a all made in the USA variant as well but untill there not avalaible im sticking making what is't.

good point however that the cam track could be made seperatly.
 
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