Feeding issues

[jambau]

So I've been running the same load in my Grendel upper for a couple years. All of a sudden it doesn't want to fully chamber the rounds. Pulling back on the charging handle to get the round out is almost impossible. If I manually feed the round and then let the bolt slam home I am able to fire the round (not slam fire) I've tried numerus other loads with no success. What do y'all think? Why won't it chamber anymore? Trim length is fine too