Behind the bench at 5:30 a.m. to continue the ogive and diameter shoot-out. There was no mirage and barely any wind so it was a great day to shoot!
The same load except for two things 1) bullets were final sized to 0.3080" - 0.3083" by running through a 0.3075" push-thru 3 or 4 times and 2) I gave the barrel a good scrubbing with JB bore paste (a mild abrasive) before shooting, and scrubbed with JB again after each group.
The theory behind the JB treatment was that maybe the shotgun pattern problem is due to fouling even though there is no significant leading seen with the borescope and no lead on patches.
One fouling shot was fired after each JB treatment, but sometimes it took 2 or 3 shots before velocities stabilized.
The ALR bullet did so-so. Shot #9 was an outlier, perhaps because the barrel was starting to foul???
The ULR bullet still made a shotgun pattern though somewhat improved compared to the previous ogive shootouts. Shots #9 and #10 were outliers, perhaps because the barrel was starting to foul???
The CLR bullet still made a shotgun pattern though somewhat improved compared to the previous ogive shootouts. Its worst outlier, the low shot, was shot #2 so I probably can't blame that on fouling???
The gas checks had been behaving themselves lately but today it threw one gas check. I'm not sure which bullet caused it or whether that bullet landed in the group.
At the end of the session I borescoped the barrel. The throat area was clean and the muzzle area was clean, but the middle of the barrel looked very dark. This photo has been enhanced to improve the contrast -- before enhancement you could not see anything other than a dark blob. Now you can see that there might be a little grey color in the corner of the groove but that's not something I would consider unusual or worrisome. I'm more worried about why everything is black?
This is the same spot in the barrel after one patch with Ed's Red. Now the lands are cleaner, but the grooves are still dark.
After a dozen or so passes with JB paste. Better, but the grooves are still darker than the lands. Thoughts:
-- the big question is why is it shooting shotgun patterns with a load that used to average 0.98"
-- due to the shotgun pattern problem, the ogive and diameter shootout hasn't told us much about which ogive is best or which diameter is best.
-- there is circumstantial evidence that the shotgun patterns may be caused by fouling -- it shot better immediately after firelapping, it shot better immediately after shooting jacketed bullets, and it shot better after cleaning with JB paste.
-- I'm not confident about the fouling theory, but I don't have any better ideas at the moment. Do you?
-- I have heard reports of carbon fouling destroying accuracy (typically with jacketed bullets), but never personally experienced it. Perhaps I have experienced it now?
-- if it is a fouling problem, then the next question is what causes it and what to do about it? Is the barrel to blame? That seems unlikely since it is a lapped Shilen. Are the cast bullets to blame? It's possible, but seems unlikely since there is almost no evidence of leading and the 2300 fps velocity should not be a big deal. I'm inclined to suspect the powder, coupled with the moderate pressure (40 - 45 ks) that doesn't allow the powder to burn as clean as it would at max pressure. Things To Try Next Time:
-- first, get the barrel squeaky clean.
-- give up on Leverevolution for a while, and try different powders.
Again, I'm not at all sure that carbon fouling is to blame for the shotgun patterns. But if the carbon fouling theory is correct, then a good cleaning and switching to a different powder should make a difference.