Well I tried different magazines,The 20 rounders that load on the right hand side first,the bolt will not lock open on.The 30 rounders that you load on the left side first,they do lock open on??I was using H4198 when it would not feed correctly.I used H335 and CFE 223 and it feeds correctly as long as I use the 30 rounders.I have about 140 rounds through it now.I even put that upper on another lower and it was better,but still did the miss feeds.I will admit I do not know a lot about AR`s.I have two 223 wyldes that I have run thousands of rounds through with no hiccups.Go figure?
Sounds like short stroking.
4198 is a fast burning powder so it may have a sharp pressure curve which drops off quick by the time it gets to the gas port. If it isn't locking back and everything is aligned correctly you may need to increase the port size IF you want to keep using 4198 at the charge weight you have tried. It's best IMO not to try to get it to cycle with the first loads you try. Work up the loads to the accuracy and velocity you want including using the powder and charge that performs best then if it doesn't lock back make the adjustment.
