Is there a way to deal with this, short of cutting and re-crowning? I’m not sure how much this affects accuracy. 20” CZ 17.7 twist from a priest 2. 
Thanks for any advice…..
Thanks for any advice…..
Tuning Dealing with barrel defects
- Thread starter Scotty1
- Start date
If I'm seeing the problem correctly, there's damage to the land(s) about 1.5-2mm past the crown chamfer. If that's right, then that looks pretty gnarly.
If it were me, I would go in there 45 degrees until that nastiness is gone and the rifling is perfectly square, and then fix the face. There should be plenty of thread left for the moderator threads.
If it were me, I would go in there 45 degrees until that nastiness is gone and the rifling is perfectly square, and then fix the face. There should be plenty of thread left for the moderator threads.
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Agreed, applying a deep bevel is probably your best bet. My concern is the difficulty keeping it concentric. No harm trying given its current state. If it doesn’t pan out, all you’ve lost is your time. Can still get it chopped and crowned.
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More of my experience is with powder burners so this may not apply. Many rifles were countersunk with the actual "crown" deeper than the end of the barrel. Essentially to protect the crown from damage (ie hunting and military rifles) if the 45 degree crown gets past the damaged lands mtnGhost's suggestion would work in my mind. I had this done to a rifle I loaned to my brother, he messed up the crown. Unless this wouldn't work on a pellet gun.
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Okay, thanks for the response’s. So it’s worse than I thought…the single land, and you can see the same line beginning on the next. I’m curious how this happened, as it is a well used/abused gun. I can afford to lose the end, as the mod sits on the shroud and these threads are only for an unnecessary barrel removal tool. Bummer.
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If you put a Q-tip in the bore, it'll reflect a lot more light and help you see everything better.
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Thanks, my pic was the old one handed iPhone juggle. I’ll get some better shots. I could barely feel that ridge with a probe.
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Perfectly concentric scoring is almost certainly from a piloted crowning tool. Shavings or some other contamination gets trapped and damages the bore as it spins.
Even an 800lb gorilla would have a hard time pulling off that trick with a cleaning rod.
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The gun actually shoots pretty well, I wonder how much better it could be with that corrected. The rest of the barrel looks great.
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Of it shoots good. Maybe leave it alone. If you have a lathe, Chuck it up and get to it. I had a bad crown on my barrel. Way worse than than. Chucked it in other and did 11° target crown. Then polished with 1000 grit set dry paper. Works great now
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Yeah my guess would be a dirty live piloted crown chamfering tool.
I'm also not sure if RTI has CZ machine their barrels for them A-Z like Taipan does, but I know that CZ blues them afterwards. Those threads are blued, so I'd wager a bet that the crown chamfer was too.
Now if RTI does have CZ doing all of their barrel machine work for them, then it's a known fact that CZ screws up the crown chamfers at the factory, leaving that nasty burr behind. In that case, it's plausible that RTI removed the burr and made that mistake.
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In my experience,
Bluing the bore of an airgun barrel is not good. Yes, most barrel bores ARE blued, but most good MATCH barrels are not. Bluing prep chemicals and bluing salts can etch bores and degrade accuracy.
A slightly unrelated thought to the op’s post, but still …..
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They don't blue the bore. Just the exterior areas where machine work has been performed (to include the muzzle face).
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I had the same problem.Get on extreme airguns on youtube and polish your barrel the exact way he tells you. It wont femove all or the machine marks .But it will soot like there not there.My group at 100 yards went from 2 1/2 inches to 1 1/4 inch at 100.Get on you tube and do it .you wont be sorry.
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