The problem with the Bushy Factory pistols is a combination of factors.
Partly it is due to the design. (Bushy is not totally responsible , as they did not design it ,
Professional Ordnance did)
Your standard AR15 will work with any good 5.56 cartridge ; most will work with commercial
.223 ammo , EVEN WOLF
.
If you shorten the barrel , about the only thing you need to play with is the gas port size ,
This is why MOST home built AR pistols WORK , as long as the Barrel is ported correctly.
When you start playing around with Bolt carrier weight - buffer weight and travel , and spring
length/poundage- you are asking for trouble.
You may get a gun which works fine , OR , You may end up with a gun which only functions with one or two brands of ammo - or one which chokes on a little fouling.