Id recommend against getting any Radical Firearms uppers, not just the .224... Ive had a few and theyre very hit and miss in any caliber. Ive got a 20" 450 of theirs that will shoot sub moa groups at 100yds with just a 2-7x scope, and a 8.5" .300BLK thatll do the same with a 1-6x scope but Ive also got a 12.7x42 "50 beowulf" that absolutely will not cycle the 2nd round... It will load the 1st one out of the mag 80% of the time and will eject it but absolutely will not chamber the next round and Ive tried EVERYTHING from new bolt, new BCG, different mags and ammo, different buffers and springs, polishing feed ramp and anything else you can think of to make it work that what I ordered the 16" 450 barrel from Bear Creek for to swap out the 50 jamomatic and get some use out of it. Ive heard A LOT of other bad things about Radical from other people as well.