Originally Posted by avenues165
You could put together an 18" SS barreled AR with a rifle-length gas system and a fixed A2 stock. There are some really nice 18" rifle length gas uppers out there. BCM makes some that I covet sooo much. A rifle length gas system should be a soft shooter, and even a mid weight profile would shoot very nice groups. BCM SS410 barreled uppers are known for shooting subMOA groups with the right trigger, optic, and ammo. They'll shoot both 5.56 and .223, they're well priced, and they're high quality.
So an 18" will have the standard rifle gas system, just like a 20? Is that generally true, or just with some 18"? (edited: already answered by WoodenPlank).
At this point of my learning, I can envision a full length rifle setup, full handguard, full stock, fixed or detachable handle, 18" or 20" barrel.
A detachable handle and 18" barrel both make sense to me. So does a heavy stainless barrel if it is noted for accuracy.
Not sure on the twist yet.