Its been awhile since I've posted here, but I just completed a project that I have been working on for several years, and thought I would share it here...
My idea was to build a 7.62x25 AK conversion using parts that I had available from many years of home gunsmithing, as well as readily available stock and materials from my shop. I decided that a bullpup would make some sense from the standpoint of compactness- I didn't really want a full sized AK in a pistol caliber. I wanted it to work with unmodified PPS 43 magazines, fullfill the minimum barrel and OAL legality requirements, and have the ability to utilize as many aftermarked parts and accessories (sights, optics, lights, grips, whatever) as possible.
I spent some time working out the details and geometry of the front end, as I saw this as the weak point on many bullpup conversions, particularly the problem of how to incorporate good sights to the basic AK platform. My solution was to build a stable platform for the incorporation of a picatinny rail on which could be mounted good aftermarket AR type removeable sights. I wanted to keep the sight radius as long as possible, and this determined the length of the basic front end components. It also left room for supplementary rails that can be used for other application (foregrip, lights, sling mounting points, etc.)
Another problem area for the bullpup was, of course fire control. I used a lightly modified AK fire control group in the (5.56 Saiga) receiver, actuated by a completely contined front trigger pack with a primary safety, and linked by a pull/pull cable under constant tension provided by the AK hammer spring. This turned out quite well with a trigger weight of about 7 pounds, a fairly short pull and crisp break, and a positive reset. AK fire control components are very good for this since the sear sufaces are large and provide a lot of room for adjustment. The trigger is adjustable and sets the length of engagement between the rear trigger carriage hook and the hammer. The primary safety block movement of the trigger, and is actuated by a lever near the right front of the trigger guard. The AK "clacker" safety is still fully functional as well.
The weapon is gas operated, and uses unmodifed AK hammer and recoil springs. The bolt carrier is slightly lightened, but would probabally work fine with no modifications other than the necessary adaptation to a very short (~1") piston. It runs very well- I have about 500 rounds through it at this stage. Reliability is excellent, ejection is very positive, and it actually runs quite clean with the several available varieties of surplus ammunition. Anyway, thanks for looking, and I hope some might find this useful...