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With the right twist for the right distance, phenomenal. Built 14 twist 25" Shilen on trued Remington 700. As stated elsewhere, first 1000 rounds, a barely even jagged hole.
14 twist up to 55 grain manufacturer recommended but my best was with 52 Bergers. 53's, not quite as accurate for me. Others I know mostly shoot 8 twist up to 800 yards. That is the limit of my experiences in that regard.
You really need to know that overbores such as the .22br has a serious issue with carbon in the first few inches of the bore. If you do not address this frequently, your accuracy will fall off, seemingly inexplicably. At 2000 rounds, when I first discovered this, I removed the carbon and accuracy improved. But not much. That is, in my group's experience, the limit of expected accuracy, with 700 being more common. That is the nature of overbores: narrow neck, high velocity and pressure, etc.
I rethroated it but the rifling was past its prime so am now going to rebarrel with an 8 twist. Got bored with 100 yards anyway, and that's when to consider the 8 twist. Food for thought: if you go ahead with this build, you can expect real accuracy at 100 yards to ~300 yards (14 twist). Keep the carbon out ahead of the chamber and if you want to rethroat it, do so at the first sign of group deterioration.
If you go with an 8 twist, you can expect real accuracy, depending, of course, on bullet selection (100 to 800, best of both worlds, 14/8) . Sierra 80 MKs!, Berger 80 Target (different jacket than Varmint to stand up to velocities that often reach 3600-4000) fps.
My experience only:
Varget, was my favorite-temp tolerant, Extreme powder, a little too slow for .22, just right for my 6br., but still fair results and shoots in so many calibers, that is convenient.- If you go to heavier bullets in, say, an 8 twist, Varget is, IMO, ideal. Light bullet: H322, i.e.; Heavy bullets: Varget.
H322, really excellent in the .22br, .204. Hotter seems to be what the .22br needs. Experimentation should prove this out, but then I am talking about scrutinizing the results. Would discourage much fiddling with primer pockets and flash holes and be sure and get small decapper pins for Lapua cases. They may or may not ship with the die, depending upon policy and you need to ask beforehand.
Benchmark, one of Hodgdon's Extreme powders; similar result as H322, some use IMR (lot variances often) and Vihtavuori N135, expensive but accurate
Flat bottom bullets for under 300 yards. Boattails beyond. Flat bottoms leave less opportunity in production for variance, in that there are fewer angles to be formed.
Primers:
CCI 450s (shooters have their own favorites) gets you into magnum world so be aware it may vary what you need for loads, save a lot of money over Br4s though I shoot Br4s in my 6br, always. Br4s in this caliber are, IMO, unnecessary expense with questionable benefit.
My thoughts: 100 yard becomes less interesting once you have mastered the single hole pursuit. 14 twist. Competition shooters oftentimes shoot even slower twist for highest obtainable accuracy from a flat bottom bullet.
8 twist leaves your options open. Will shoot 100 out to 800, beyond...?
Load development is easy. 80 grain Sierra Matchking in twist really accurate
Brass, Lapua 6br:
Unsure what you know about .22br so:
Lapua 6br brass run through .22br die but preferably after running a mandrel through the neck first to stretch out and smooth before the next step of full length sizing.
There will be a bulge at the NSJ. Some ream the inside of the neck, some turn the bulge off just up to the NSJ, and some leave it, as long as it is below where your bullets seat. If you turn them and have them annealed via, for example AMP annealer, be sure and tell the annealer because the neck is thinner and requires a different code/heat.
Build:
Be aware that Lapua 6br brass has a small primer hole and small primer pocket-small rifle primers; because of these factors, you should get small (or turn your own) decap pins to accommodate Lapua holes;
I don't even know for sure if this is optional; have gunsmith turn down firing pin and bush to prevent gas escapement and primer deformation.
Lots more, please do ask if you wish.
"We're all in this together." (Red Green)
Best of luck. Keep us informed of your choice and progress.
"The closest thing we have in my hometown is a 300 pound Avon lady."
