There isn't very much info on just the uppers.
The new ones that are being sold as Upper conversions use a different mag then the complete gun uses.
I have an upper coming and UPS says it will arrive Wednesday. I have plans to re-do some of the stuff IF I can. Just add a rifle length set of 2 piece railed handguards, etc....
I wish I knew what the muzzle thread size is?
Anyway, I plan to do a range outting this coming weekend and already have a few different manufacturer's ammo to test.
One thing, the mag for the upper conversion is shorter, because it fits in a standard AR lower....so, some of the 2.5" shells that work in the complet gun, do not fit in this mag. Seems if the OAL of the cartridge is under 2.300" it should fit in the mag.
I want the next couple days to pass quickly