Well, after a month and a half without my rifle (back to Remington for lack of complete rifling) I finally got it back. I've now had a chance to take it to the range with 20 rounds of pb Ranch Dog 425s. Unlike my previous trip which resulted in disastrous leading and the discovery of the rifling problem, I came out reasonably well this time.
A happy sight!
However, I'm still having a few issues. First of all, there still appears to be a little leading. My groove diameter measures .457, but that is with calipers (haven't slugged yet for fear of damaging the bluing, but plan on figuring out a way soon to confirm the measurement). I'm using, as mentioned, Ranch Dog 425 grain boolits with the plain base cutout. They are lubed with White Label Xlox 2500, sized to .460, and loaded over 29 grains of 5744 with no filler for around 1350-1400fps (no chrono yet to confirm that). Here's a couple pictures of the mild leading.
Besides that, the accuracy seems mediocre. Now, I have been a bit out of practice and some of this is DEFINITELY the shooter, but I'm fairly certain there's more to it than that. I can usually call a shot when I pull it off, and some of these seemed to be in the opposite direction from my expectation.
Here's the first target. The circled holes were shot after zeroing scope - others were still in progress (after the first couple in the dirt). All shots at 100 yards, and the pictures are sideways but still show groups well.
After zeroing, I shot at this target. It already had some (seemingly .30 cal) holes, so I circled mine in case nobody could tell by the size .
The gun was not allowed to cool between any of the 20 total shots, but they were not fired rapidly either. I'm fairly certain, accounting for the shooter, that the gun is shooting 3-4 MOA currently, and I know it can be better - but first the rest of that leading needs to be gone.
It's possible there are barrel constrictions from the dovetail cuts which fire lapping could improve, something I can confirm with a barrel slugging if I can feel it. Maybe I should go ahead and lap it anyway? It's also possible that there was still some copper fouling that caused the small amount of leading seen. It was test fired at the factory (3 rounds, jacketed) and not cleaned before being sent to me, and I only had Breakfree CLP and a boresnake with me to clean it beforehand. Those did seem to get it pretty clean, but it's plenty possible that wasn't quite enough.
I noticed some gray residue around the muzzle and in the barrel after the first couple of shots that I feared was leading, but it wiped off with my finger. I'm thinking it was powder residue sticking with some of the bullet lube, and it made a bit of a "star" around the muzzle which wiped away easily. Those bullets were dip lubed over the stove and WELL over-lubed I believe (no chances taken!), so it would make sense that this is the case.
In any case, I'm open to and greatly appreciate any suggestions as to where to go from here to improve accuracy (shooter improvement is taken as a given and will occur rapidly with my current excitement to get out and shoot this beauty, so other suggestions preferred ). I'd also like to once again thank everyone from my previous, now old, thread who got my started on the right path - it's been a lot of fun putting this new load together. I also just picked up some gas checks and will be looking forward to some stronger loads using IMR 3031 and GC'd Ranch Dog 425s!