My first build on the AR-.308. I've built several AR-15's in different calibers but this is the first time I've encountered trouble after pulling back the charging handle, about mid-way I encounter a bit of friction (not smooth) and when the bullet is fully chambered, it is very hard to pull the bolt carrier back with the charging handle to eject the round. I've one from the silent buffer tube from JP (i think) to a rifle spring with .308 buffer tube. I tried a different bolt carrier, and different charging handles. Anyone have any thoughts on what's next? Also changed out the take-down and pivot pins.