Did you ever get better groups after re-crowning a barrel even though you couldnt' see a bad crown?


I have 3 barrels for the Knight KP-1 breakopen. They group like crap. 4-5 inch.

I tried no forend, pressure under the front of the forend. No change.

So tonight I took the .223 barrel and my handle barrel crowning kit and put a 45deg crown on it.

If my 3 barrels have bad crowns then all of then do??

wish me luck.

Okay, you're wished.

Twenty-some years ago Clyde Rose (RIP) was working the warranty station for Browning in StL. He was in charge of the BLR and BAR returns. His boss told him the standard thing was to cut 1/8th to 1/4th of an inch off the barrel and recrown. It fixed about 90% of the accuracy issues. Barrel Harmonics was the culprit. I visited him at Browning in Utah, where he was doing much the same thing. He got the idea to add mass to the barrel that was movable to adjust harmonics. It started out about the size of a bratwurst, and became the BOSS. He made a lot of money assigning the patents to Browning/Winchester.

I wrote a lengthy article for Precision Shooting Magazine on the theory and practice. Ron Hoehn is a Bench Rest shooter in the St Louis area. He offers a barrel tuner. The tuner fits on the muzzle end, and has a sleeve in a cylinder appearance. It is graduated, like a BR powder measure. You loosen the nut, and rotate the outer cylinder in or out, tighten the nut, and shoot. As you move it, groups get tighter. At a certain point, they begin to open up. Then you back up to the "sweet spot" and secure the collar.

Anyway, that is the physics of the crown thing, probably more information than you ever wanted.

regards,

Rich

Strangely enough, I wrote a SHORT article for PS magazine, somewheres around 2005, arguing that boattail bullets wear the crown more than flatbase, and are more affected by bad crowns. It was a do it yourself article on how to use the Brownells 120Deg crowning tool to recrown the barrel. I had two barrels, that were losing accuracy, and the recrown put the groups back into the 3/8" size. It's a cheap idea to try, besides rebedding the action.

quote:

Originally posted by richj:
Did you ever get better groups after re-crowning a barrel even though you couldnt' see a bad crown?

Yes, weekly. If you know what to look for, bad crowns are relatively easy to spot. And the majority of new factory barrels have bad crowns. All of these will benefit from a good recrowning job. Best tool for those without access to a lathe is the Manson tool.

quote:

Originally posted by Lanny from NY:
Strangely enough, I wrote a SHORT article for PS magazine, somewheres around 2005, arguing that boattail bullets wear the crown more than flatbase,

How does a boat tail bullet produce wear at the muzzle?

My theory was that the muzzle is exposed to gas erosion for a longer time with each shot with boattails, and that the forces of pressure variations on the bullet base are exerted for a longer time on a larger surface area than a flatbase. Basically, before you rebarrel, or set back and rechamber, try recrowning first.

I read an article somewhere, don´t remember where, where the author sawed tho barrel at various degrees and without deburring of any kind.
If I remember correctly this had little effect on accuracy. Mind you this was not on a bench rest rifle.
Any one see this?

quote:

Originally posted by Ossi_Iceland:
I read an article somewhere, don´t remember where, where the author sawed tho barrel at various degrees and without deburring of any kind.
If I remember correctly this had little effect on accuracy. Mind you this was not on a bench rest rifle.
Any one see this?

Yep. About the only thing that was affected was the POI of the groups as the angle of the cut muzzle changed with each cut. Each succeeding group's movement was a more-or-less exact replica of the direction of the muzzle's new angle.

IIRC, both Harry Pope and Dr Franklin Mann investigated this phenomenon back before WW1.

BTW the angled-muzzle method of changing POI has been used at least occasionally to adjust the POI of both double shotguns and double rifles.
Regards, Joe

quote:

Originally posted by J.D.Steele:

quote:

Originally posted by Ossi_Iceland:
I read an article somewhere, don´t remember where, where the author sawed tho barrel at various degrees and without deburring of any kind.
If I remember correctly this had little effect on accuracy. Mind you this was not on a bench rest rifle.
Any one see this?

Yep. About the only thing that was affected was the POI of the groups as the angle of the cut muzzle changed with each cut. Each succeeding group's movement was a more-or-less exact replica of the direction of the muzzle's new angle.

IIRC, both Harry Pope and Dr Franklin Mann investigated this phenomenon back before WW1.

BTW the angled-muzzle method of changing POI has been used at least occasionally to adjust the POI of both double shotguns and double rifles.
Regards, Joe

I think P.O.Ackley also tried that one.

I have always gotten better accuracy when I've re-crowned. Frequently dramatically better.

Over the years I've "cut & crowned" probably a half dozen or so barrels using the old Bubba method, ie, the hacksaw, files, and stone/hone. Most shot better, none shot any worse.