Brother dropped off his 450 AR before deer season for me to look at. Said shooting at target it works pretty good but every time he shoots a deer it has a failure to feed. I've never had an issue with an ar FTF but maybe a different weight buffer? I initially thought mag but he is using factory mag(spring seems very stiff) and a PMAG i converted for him(spring seems pretty soft) and they both act the same. Using both Hornady loaded ammo and some handloads i made for him and having problems with both. Thanks SB