I would prefer some modifications to the design. Namely the already mentioned barrel block latch, I have no issue with how it works, but the projecting tab would annoy me...im not sure what change to make there, but its functional enough for now imo.
I'll ponder how I might want to change that. But TBH, the couple of comments in this thread are the first to take issue with it. Maybe it looks particularly obtrusive in the photos? No one who has handled or shot it has mentioned the latch at all.
A production version could end up with quite a few changes. Remember, I built this for me, so it is the way I want it. I was not trying to develop a rifle to take to market, but with folks quite literally begging me to build them and me not being able to do so for several reasons, I felt I should approach manufacturers with this concept, and it would be great to have some idea what kind of money people would be willing to pay. There are a number of carbines on the market, but only one other folder, and none this light (the Sub-2K is 3/4 pound (21%) heavier, despite being mostly polymer)
I would also think that a possible increase in bolt weight might help longevity and reliability. Also having other chamberings even if this required the receiver be upsized a bit.
Eh, the rest of the rifle is tuned to the light bolt. A heavier bolt would allow for a lighter recoil spring and thus lower cocking effort, but that's about it. This one is heavy enough to keep the breech closed even with +P loads, and the spring arrangement decelerates it very effectively. I had it at a local range on Sunday, and one of the managers tried it out. He said despite the thin butt plate and light weight, it actually had a lighter felt recoil than the Sub-2K. I know the Beretta storm I had was obnoxious with that ridiculously heavy bolt slamming into the polymer receiver.
As for other chamberings, they're just not very popular. We rarely see .40 or .45 carbines on the shelves here. Beretta has dropped the .45 ACP offering in the Cx4. Most AR PCCs are 9mm. The Skorpion is only offered in 9mm. .40 popularity has been waning for awhile, and .45 is just too expensive to shoot for many. 10mm is even more niche and more expensive, relatively few people jumping on that band wagon, despite the impressive ballistics of the cartridge.
As a 10mm nut, I will probably build a 10mm version for me, but it's not gonna be blowback. True direct impingement or short stroke piston gas operation.
Having some Magazine modularity would be good, but off the shelf probably most guys want glock mags as stated...it really dosent mater at this point, lets all just assume it take the mags we want it to.
Important to keep in mind. As I said before, it made sense for me to use the magazines I did. But with the mag well outside of the grip, the potential mag configurations are limitless. Everything from single stack subcompact mags to Glock, Uzi, MP5. Not trying to do a grip well, there are no constraints on the dimensions and shape of mags that can be made to work.