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Can you make a centre drilled brass pin which is a good fit in the bore to ensure good centering?
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Diagnosing a bullet strike
- Thread starter cdhknives
- Start date
Can you make a centre drilled brass pin which is a good fit in the bore to ensure good centering?
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- Apr 12, 2013
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- 560
Update: Using a brass bore plug for a tailstock dead center point and the chamber as a headstock center point, plus a driving dog/plate combo I turned new threads behind the existing threads. When I measured dead center of the Class 3A thread spec I stopped, reset with steady rest and chuck, parted off the old threads, did a quick flat crown, and tested my brake. It was a very tight fit, install-able by hand for about half the threads and using a wrench to easily run on the rest of the way. A 50 yard quick range test showed improvement but I need to test it at 100 yards to confirm. That may be as soon as today...
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- Apr 12, 2013
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Meh, holes in target still have tails at 100 yards. Groups are 12"+ too. With and without suppressor, with and without flash hider/suppressor mount. I never bothered to try the muzzle brake.
Getting really close to tossing this barrel in the scrap heap...need to go back and try some supersonic loads and see if it is a low velocity issue.
Getting really close to tossing this barrel in the scrap heap...need to go back and try some supersonic loads and see if it is a low velocity issue.
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That means the twist is too slow for the length of bullet you are using.
http://www.bergerbullets.com/twist-rate-calculator/
http://www.bergerbullets.com/twist-rate-calculator/
Don't toss the barrel, as mentioned above, please let us know what bullet you are using, barrel length and twist rate, freebore of chamber, powder, and muzzle velocity if you know it.
I have been experimenting with a 300 Fireball using lightest 30 cal bullets in a 1:15 twist barrel and it shoots 5 shots under 1/2'' at 100 yds.
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- Apr 12, 2013
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Been down this road. I'll review for y'all. 220 grain Nosler match bullets. Cerrosafe castings confirm muzzle bore&land, and chamber dims are on spec. Twist rate is 1:8, confirmed by measurement (tight patch on a cleaning rod). The berger calc gives a 1.91 with 1.5 or greater being fully stable. 1:8 twist should stabilize this 220 grain bullet down to under 500 fps (1.5 stability factor per Berger). I am chrony measured at 950-1000, which meshes well with Hodgdon published reload data. Scatter on the target is 'shotgunning', not stringing from velocity or scope issues. Tails on holes are random as well. Full power 110-170 grain bullets seem to work okay based on offhand plinking, not bench testing. I need to confirm this with more controlled testing. I can also run some 180 and 240 grain match subs and supers but this is getting tedious...gotta check velocity on each to confirm subsonic conditions. Rifle is a 10" AR15 SBR with disabled gas system (no tube, reversed gas block to cover gas port) and side charging upper...straight pull action basically. Bullets measure ok, NOT undersized. Running out of ideas...
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- Apr 12, 2013
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I have wood blocks and lead shot filled leather shooting bags, and our club has very sturdy T shaped shooting benches on concrete pads. Barrel is free floated, resting on a tubular handguard. I've been fairly hardcore reloading and shooting for about 20 years now...just getting into lathe work the last few years and gunsmithing is a natural outgrowth of that. I can swap the barrel to another upper receiver with a different scope, but I bet the problem follows the barrel. Dang, really thought the threads would fix the problem!
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