Will a 1/7 twist barrel not last as long as a 1/9 twist?

I have heard that the bullet can actually "skip" across the rifling near the throat for a little bit before it is fully "gripped" by the rifling, and that this causes increased throat wear.

I am especially concerned about wear and accuracy with hot-loaded 55-grain bullets out of a full length 20" barrel.

Also, has anyone had any problems with DPMS rifles or lower receivers?

The DPMS uppers I have and have shot from CMMG run better than anyother AR uppers I have or ever shot. I wouls say they are just as good as Colt. IMHO ofcourse

My DPMS CMMG 1:7 Upper hicuped on the first two rounds (Failures to extract). Since then it has been 100% relaible.