horizontal magazines are okay as long as you get rid of that integrated rotating ramp on each magazine (ie, make it a standard double stack mag that is simply fed into the weapon at a perpendicular angle). I would think that the means to do it would be simpler than the G11.
The firepower needs to be increased by at least 1/3 over what a .357sig offers. Also making the gun "fat" isnt much of an issue because someone else designed a fkkin 12 Gauge shotgun that used the same style of magazines along with the built in rotating ramp. It never went anywhere but from the looks of it this didnt impact its handling any.
In a PDW im mainly concerned about Firepower, the ability to preserve that force of impact at 200 yards so that it will still hit like a 9mm at point blank range. Which is also related to making sure that it can reliably reach 200 yards.>>37153993
Yeah but then again a .357 sig is like the 7.5 FK except its not as long. The main issue is Width since the casing is probably about 11mm wide. The standard .223 case is 10mm wide, while a 5.7x28 case is only 8mm wide. Width determines how many more rounds you can put in the magazine and when it comes to PDWs you want as many as you possibly can cram in there.
Also making it use 5.56mm would appeal to military jarheads who cant-into logistics management. They dont want to be issuing another caliber and making sure that it gets circulated everywhere to all the airforce and military bases we've got.
If the gun can bust a 5.56mm cap, even if it screws its range and has a reputation for being as loud as a machinegun, then it can USE off the shelf ammunition. The faster burning snowflake 5.56 can then be issued and requested at liesure.> its one of those "if its an emergency and you gotta do it, this thing can do it" which is actually a pretty nice selling point to the military
Also using STANAG mags is a similar plus. You'd want to use a drum with a PDW though. All yer rounds in one package.