This spring I put together a new AR-15 in 450 Bushmaster. It is based upon an 80% lower with a JARD AR15 #4 trigger and a JSE upper with 18" barrel in 450 Bushmaster. The magazines are the 20rnd 223 version by Lancer. When factory ammo from Hornady is used everything works fine. However, when using reloaded ammo there are consistent failures to feed due to incomplete cycling. The bolt fails to pick up the next round and either closes on an empty chamber or hangs up on the top of the next round. The last round in the magazine ejects but the bolt does not lock open. I am using the Hornady brass and Hornady 225gr and 250gr bullets on top of IMR 4227 up to the maximum loads recommended by Lyman. I do not want to exceed recommendations for fear of damaging the rifle. What are the things that can be done to allow lighter loads to function while still safely handling factory ammo?
I have been reloading for close to fifty years but this is my first experience with semi-auto/AR-15 rifles and these kind of problems baffle me.
Thank you