FWIW my friend has a flat plug and I have a deep concave plug so he decided to call up T/C to find out what the story was on the differences. The T/C rep said that the deep concave plug was T/C attempt to get rid of the dreaded crud ring problem,especially when using T-7 pellets. When my friend asked him if it was successful and should he switch the rep was vague with his answer. What I got out of the conversation was that the plug change really did not do much for the crud ring problem. It did sound like the deep concave plug is more suited to pellets(no crushing of pellets) but loose powder works fine too. The flat one is fine for loose powder but pellets may get crushed when using this design therefore they decided to keep this design change.This year I did not shoot my omega during BP season so I just popped out the breech plug and the pellets came out whole along with the PB.Just wanted to say that all this info. was told tomy friend by a T/C rep therefore I felt I would pass it along.