Though it is no doubt a creative and original design, even the improved version strikes me as rather unergonomic and technically too complicated. One of the main things a standard issue rifle needs is to be effective, but not too complicated to assemble/disaassemble if one needs to check it or repair it in a short amount of time. A gravity-fed magazine, like on some OTL bipod machine guns, is certainly doable, but for an assault rifle, it's a little too unconventional. If upside-down gun construction was so easy and reliable, especially for mass-produced, standard issue firearms, you'd see a lot more of it in OTL.
As I mentioned I know very little about gun and gun design despite the fact, somewhat embarrassingly, that in my army cadet time I actually got a marksman qualification.
I do appreciate you guys' suggestions since I'd rather have a minimum of plausibility while at the same time having WTO and NorAtPac forces both have a half familiar / half distinctive appearance compared to the OTL counterpart.
About the ergonomic aspect, it occur to me that one advantage could be in regard to the recoil. Unlike normal "main body on top" rifles where it is absorbed back in a straight line, the canon being lower would actually make it be absorbed up and diagonally and diffused on a slightly larger surface. At the same time, one downside from this design that simultaneously occurs me is that repeated firing would have a tendency to increasingly go downward for the same reason. I wonder if there would be a way to compensate for that ?
Regarding the feeding system, is a gravity fed system more complicated then one that push up bullets or is the gravity system worse for other reason like for example jamming ? As you said that type of magazine placement is clearly not popular OTL but depending if it's a cost or effectiveness problem, It might be justified in story: A less efficient but cheaper rifle could simply be the result of a government contract going to the lowest bidder who achieve this bid only by cutting corner.
Also, is the added complexity of a gun like the one I showed because the grip-&-trigger system is on top ? I wonder if it would make a big difference if it was a single large piece of metal with only the 2 hand grips having a wood/plastic covering ? Similarly, would a single piece shaped butt take down the apparent complexity ?
One last question, while I can see the disadvantages, can anyone think of advantages for this type of design ? The reason why I like this design is entirely aesthetic but I assume that those who made the Konstantinov SA-01 must have thought, even if they were later proven wrong, that it could help in some ways. The only thing I can come up, and not a huge one, is that since the casings would be ejected lower, it might solve the problem of left-handed soldiers using a gun that eject right since the casings wouldn't fly across their field of vision.
There were some Kalashnikov and other rifle bullpup projects developed in the East Block in OTL. If you want, I can show you the prototype of the Sa-58 bullpup variant, or a Soviet Korobov SMG.
cheers for that.
Googling Korobov, the TKB-022P & TKB-022PM look interesting but because in terms of look they seem closer to weapons that only became common decades later (the feeling being stronger because of the tiny barrel), I'm afraid that using them will look like I'm introducing advance weaponry to the Warsaw Treaty Organisation in the mid-20th century, regardless of their historical existence, verisimilitude and all that. The TKB-022 somewhat doesn't feel visually distinctive enough compared to an OTL AK-47 but the TKB-408 on the other hand is closer to what I have in mind.
regarding the Sa-58, is this the one you meant ?
It's further away from the AK-47 then the TKB-408 but since the standard weapon used but WTO forces is not supposed, in-story, to be based on the designs of Mikhail Kalashnikov, I could try to combine some elements of both.