Ok, here are a few more details: If I can load 180gr or lighter bullets in while maintaining an OAL shorter than a 223, I can use AR-15 or modified AK-74 magazines and save a world of trouble trying to design and fit a new magazine (which would probably be based on the AK-74 as well).
The critical parts of this rifle are from an AMD-65 kit, using a full length Marlin 336 barrel turned down to fit the AK trunion. The receiver is still up in the air, partly because I've been unsure what magazine system I'd use. If I had a tilt locking system like the Mini-14 and AK, I could use a stamped receiver. If I'll be using a straight insertion, side locking AR-15 mag, I'll definitely use a milled receiver of my own design, which will accomodate certain steel parts like the original front and rear trunions, as well as an extractor and possibly more, like rail inserts.
I've put a 180gr 357 bullet into an empty case by hand, and if I line the case mouth up with the front crimping band, it's shorter than a 223 OAL, which means I could use an AR-15 magazine to feed it with few if any modifications. But that would rule out using factory loaded 35 Remington (except single shot), so there's a drawback.
I'd want pressure curves to match the factory ones for safety and functional reasons, so if seating depth affects it significantly, I'd need to adjust for that.
My goal of this system is actually to display the merits of a 35 caliber intermediate round in a semi-auto for hunting, personal defense, and law enforcement. This is in order to introduce a wildcat with similar ballistics but using modern pressures and in a shorter case that would have an OAL equal to or under the 223 even with longer 358 bullets. Since we can't hunt with semi-autos in PA, finding a good hunting load can come down the line. In the long run, I'm also looking into making a box magazine fed pump or levergun for intermediate length rounds, which could include this wildcat for PA hunting.
Even the full length 35 Remington has been successfully used on a standard length AK platform (as well as the 308, though with a beefed up bolt and trunion). Even if stuck with full length rounds I could make it work, and that would have its advantages. I'd just need to invent my own magazine, or drastically modify an existing one, which is possible. But using AR mags would be the cats' meow.
