My wife and children were gone for four days last week. So I decided to tackle this project while I had time for myself. I must give credit to the following people on this board for information and inspiration: JPGlee1, Pookie, KernelKrink and VIS.
Equipments: Harbor freight 7x20 lathe, hacksaw, drill press, tap and die, caliber, grinder, dremel, and belt sander (and shop vac)
Materials: Whatever was at my reach plus OOW '74 receiver, Bulgarian '74 bolt and carrier, FAL flash hider, UZI barrel, K-VAR stock and grip, 4 sten mags of various origin, Bulgarian rear tang.
1. Front trunnion. I made this out of 1 inch thick 6061 block. Drilled .625 hole for barrel and .700 hole for the carrier. The trunnion is also the rear sight housing. 4 hours.
2. Turn the barrel to .625 and press fit into the front trunion. 1 hour
3. Modified the bolt and carrier. Bolt carrier is heat treated. I could not drill or file. I cut the handle with dremel and moved back 1 inch and welded on. Since I could not drill into the carrier, I went ahead and welded the bolt to the carrier. Trim off the rear safety lug. 4 hours
4. Sten mag housing. Made this from 1.5 inch wide flat steel and 1.5 inch wide 90 degree angle (not sure what to call it) that I got from home depot. The hardest part was the mag release. Took three tries to get the right height. Even then, I have to push the magazine slightly upward before I can press the release. Need new design but it will work now. 3 hours.
5. Trimmed 1.5 inch from the front of the receiver. This was a mistake. I will explain it later. Recut the bolt release on the top left rail.
6. Put it all together. It doesn't work! Hammer does not hit the firing pin. Also, the bolt will stay back when you pull the bolt all the way back. This is because the bolt is now 1 inch shorter and will not hold the hammer down.
7. Modified the hammer to have different angle to strike the firing pin. Also smooth out the top of the hammer so it won't hold back the bolt.
8. Modified the single hook trigger. Welded small bead on the inside of the hook. So the hammer is held down little lower.
9. Shorten the cover and put it all together. Safety does not line up with the the cover.
10. Made front sight base fron 1 inch thick 2021 alumninum. Drilled 5/8 inch hole (.625) for the barrel. The base is secured by 2 8x32 socket head screws for now. Need to pin it later. I bought some front sight inserts fron TAPCO but could not find any tap will match that. So on my handy dandy lathe, I made that had 10x32 thread. Front sight adjustment is only vertical. (2 hours)
11. Made rear peep out of 2021 alumninum. The hole is 3/16 wide. Bottom part is drilled and tapped with 8x32. Two socket head screws pull from either side for horizontal adjusment. (1 hour)
12. I had STG-58 flash hider. I wanted to thread the barrel but I just could not do it. At 200 RPM, it was hard to index the lathe. I think there is info on the web how to modified this lathe to go 60 RPM. Maybe later. Instead, turned the diameter down to .585 and slip fit then use the 6x48 screw to secure it. (3 hours wasted trying to turn thread).
Lessons learned. It may work better if both front and rear part of the receiver was shortened. The trigger modification may not be needed if the bolt does not travel the same length as the '74
I do have another set of stock ('74 S type folding stock)/bolt/carrier/barrel/receiver. Not sure if I will have time to work on it.
Function tested with dummies and it failed to eject full length cartridge. It will eject an empty fine. Had to shorten the ejector tiny bit. Like I said, this may not have been a problem if the receiver of shortened from the rear also.
I don't have any feed rail. The magazine is tilted back a little bit because it is 90 degree to the bottom side of the receiver not the top. So, the cartridge points up ward in a correct angle. I had not had any stove piping while running dummys.
I drew up a quick dimension for the front trunnion blank and took it to local shop. It would cost about $20.00 for 1112 steel at quantity 1000. Much more for 4130. It is possible that I can set up for a group buy but it would take 90 days. Not sure if shot has drill size .685. Otherwise, the hole will be .625 (5/8 inch) and have to turn down the barrel.
One more thing I would like to point out is the head spacing issue. The best way to address this would be deepen the chamber about .05 so the cartridge is completely supported. If no chamber reamer is available, deepen the bolt face.
I forgot to mention of about the front handguard. Made from 2 3/4 inch thick oak veniers sandwiched together (1 hour).
Pictures are in. Thanks everyone on help how to post pics
I will have to wait until this saturday to go out to my ranch to test it out. If I have time, I will do quick test and right up a report on it.
Mag Well for Sten Magazine
Welded AK-74 Bolt
View From the Rear Peep Sight
Modified Trigger to hold down the hammer