Just to re-cap, I removed the metal covering the the flash hole channel and opened it up to .125", cleaned the carbon and re-installed.

Went to the range Sunday, and the first shot was muffled and I didn't touch the target... but the breech didn't blow out. I don't think the load was seated well enough. This was with the same Win 209 primers I was using when I had the hang fires before. All of the following 5 shots were seated tighter and they all sounded good and grouped about 1.25" at 50 yards, even though they were all different bullets and sabots. All was well till I moved out to 100 yards then the first two shots were low but close together... the next 3 shots were way wild and almost off the target. All 5 of these were 290Gr Barnes TMZ with MMP black sabots. I don't know if: the shorter MMP sabot was not stabilizing the long Barnes bullet, there was too much plastic build up from the sabots, or I was flinching after shooting my 30-06, 20 gauge slug gun, then the Omega... I've been getting to be a recoil wimp lately.

"ronlaughlin - Use the 1/8" drill to clean the flash channel, and don't swab between shots, and have a somewhat tight sabot, and be sure to have the bullet/sabot tight against the powder. You should have good ignition with any primer, if you do these things."

I cleaned between the shots with Blackhorn 209 solvent, and was getting a lot of thick black powder residue on the patches. Way more powder residue than when I used American Select… which was the cleanest shooting powder I ever used, but was prone to moisture.

That brings up the questions: whether shooting the bore dirty helps reduce the plastic in the rifling? Does shooting the bore dirty reduce or increase accuracy? How often should you clean for plastic in the barrel.

I'll have to put in more range time to find out.