Originally Posted by Mercator
...Different uppers and lowers can be mixed and matched.
Might mean that you can get a dedicated .22LR upper and pin it to your .223/5.56 lower, along with several other different dedicated uppers of various calibers if you choose.
I really like my CMMG dedicated .22LR upper because so far it has fed all of the different brands of .22 ammo I've tried with a without a hiccup.
I'm averaging groups of about an inch at 50 yards with Federal Auto Match but there may be more accurate brands that I have yet to try.
I also added an adaptor so I could use S&W MP-22 magazines that have buttons on each side to make loading those tiny rounds into the magazine a real breeze.
Also the adaptor allows the bolt to remain open with the magazine removed, just like the 5.56 upper does whereas a lot of .22LR bolts will drop when the mag. is removed.
I like the fact that I can still use my Geissele SSA-E trigger that is in my lower so there is no trigger pull difference between the .223/5.56 & the .22LR when assembled into a complete rifle.