Here's an update.
At this point, I'm a bit lost on what to do next and feel like I've lost the battle and possibly screwed up my gun. I'm feeling down and discouraged about it. I went to the range twice after making my previous changes. I used my load that has seemed to shoot really well in the past: h4350 at 57.5gr, sierra prohunter 150gr, fed gm210, win brass once fired then twice fired trimmed sorted and primer pockets cleaned. I try to get the primer seating depth as uniform as I can on all of them. I matched my bullets base to ogive with bullet comparator, then seated all bullets to within 0.002 of each other based on base-to-ogive length using bullet comparator. Out of both trips (5 sets of 4 shot groups each trip ) I think I only managed about 5 groups that were between 0.5" and 1" at 100 yards. Early in my development of this load, about 400 rounds ago, it shot this load much better.
- I ditched the buttstock ammo holder with the cheek pad because the straps on the bottom of the stock were catching on my rear rest pretty badly. But with the installation of my lower rings I can get really consistent face pressure on my stock so I'm not worried about that part anymore.
- I tried using my left hand very firmly on the foreend to control recoil. This too hard to do in a consistent way, so I ditched it since I've had good results in the past letting the gun free recoil.
So here's several things I've done that I'm wondering about and/or worried I screwed up my rifle.
1 - put in talley lightweight tikka rings torqued to talley's recommended torque but I didn't lap them because I don't have a lapping - I knocked the top half of the rings off my bench when installing them. I'm pretty sure I have the front/back halves matched, but I don't have any idea if the top halves are in the same orientation as they were in the package. Oops. Any way to figure out with these rings which direction the top halves are supposed to go? So, it's possible my scope is shifting in the rings but I don't know how to figure out if it is happening. Suggestions? I've thought about lapping the rings, but I don't want to screw them up. Would a thin layer of blue loctite on the bearing surface of the rings prevent slipping without messing up the scope?
2- I removed more of the rib closest to the receiver to make sure it wouldn't hit during recoil. I'm wondering if I now need to stabilize the foreend and bed the stock or if restarting load development would work. I don't love the idea of stabilizing and bedding because I don't want to add the weight and I also worry about the adhesion of the epoxy to the synthetic stock. And, that's another $60 in materials to potentially not gain anything. I did recently pick up an unused t3 stock pretty cheaply, so I can throw it in there and see if the rib pressure point was actually helping my accuracy.
3 - before my last trip to the range, I used jb non embedding paste on the bore to try to remove any potential carbon ring in the throat and to smooth the bore because it seems like my barrel copper fouls really easily. I used a 7mm nylon brush with an oversized patch with the paste. I put a stop at the muzzle so I didn't screw up the crown, gave it 100 strokes, cleaned the bore well, then did another 100 strokes with a fresh patch and paste, then cleaned well. After 20 rounds, it seems like I can seem MORE copper fouling near the muzzle.
4 - cleaning - about 400 rounds ago, my cleaning regimen after 20 rounds would be to use hoppes #9 on patches and about 20-30 strokes with a bronze brush. No copper removal. Awhile later I started using sharp shoot r tactical advantage with the accelerator after every 20 rounds with nylon brush and patches. I also used CLR (calcium lime rust remover) to remove built up carbon a few times. I think my barrel seems to pick up more copper than it used to. Maybe I should go back to just using Hoppes #9 and not remove copper?
Ugh, at this point I'm not sure which direction to go and I'm tired of nickel and diming myself with no improvement. I did have plans at some point to customize this gun with a nice lightweight stock (mcmillan, manners, or ag composite) and an aftermarket 24" barrel of the same contour. I guess I could also sell this one and get the newer tikka in od green that has a 24" barrel. I just got a raise at work, so maybe I should just expedite my customizing and I wouldn't have to worry about fiddling with the factory stock or copper in my barrel. But, that would be extremely pricey. Feeling lost and defeated and my trips to the range are now just frustrating.