Been a while since I've posted. The ah-ha moment resulting from borescoping the barrel looks like it may be more of another false lead. To summarize, I tried some oversized 311xxx bullets. Moulds thru 0.312 slugs and sized them to 0.312 as that was the largest sizing die I had. Moved to NRA 50/50 lube, which is a love more enjoyable to use since it does not ooze out below the bullet as my BP lube does. But still my flyers continued and beyond 300 yds they were major flyers. Granted, some of the shooting conditions did not help. But I'm shooting with a very experienced Cl F shooter and damn fine spotter so we are pretty good as sussing out the conditions and the corrections.
From the start of this, I wanted to try a fatter bullet. Challenge was finding someone with a mould I could borrow and a sizing die. A few weeks ago, another member had 3 rounds left over and asked me if I wanted to try them. They were the 314299 bullet over 13.5 of Herco. He shoots an Enfield that is so shot out that the rifling is all rounded. The fat bullet made it shoot again. I took those 3 rounds and fired at a 4 inch pipe at the 500 yd berm. I'd had flyers that day that spanned beyond the ram. I put all 3 rounds into the dirt in about a 4 inch circle. Granted, only 3 rounds, but very promising.
I finally was able to get fellow shooter and gunsmith to dig thru his huge assortment of moulds and find a 314299 that "he knew was in their somewhere". He also had the 0.314 sizing die. Loaded up 60 rounds for a 40 round match.
The shoot was what we call the VT match. Round plates at 100, 150, 200 and 300 yds, each sized to cover the same minutes of angle. There is a meerkat at 400 that is shot offhand as a tie breaker if required. Plus you get a nice pewter pin for every meerkat you manage to dispatch.
Cutting to the chase, the rifle shot some truly stunning groups all the way out to 300 yds. No flyers of any kind. At 300, my spotter could only tell me I hit the target because the bullets all were in the same group and there was no longer any paint to mark the spot. Shot a perfect score of 40 and hit one of the two meerkats. Another thing I did was drop my velocity by lowering the powder charge to 17gr of 2400. I did not put them over the chrono since I did not have time. But I'm guestimating that they are in the 1400+ fps range.
So, it appears that properly filling the bore, regardless of the pitting, has solved 95% of the problem. I say 95% because I have not shot it off the bench at 500 yds yet to see how it groups. That will happen shortly.
I just took delivery of a new NOE mould in their version of the 314299. It is currently seasoning in my oven in prep for casting some bullets. I still have some from the Lyman mould I used last week so I'll shoot those at the next match. But I'm itchy to get some out of this new mould.
I'll report back with results.