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Old 01-07-2020, 11:23 PM
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Barrel Crown Question



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I've seen a lot of discussion about barrel crown affecting accuracy. I've been shooting for a number of years, but have only recently gotten to a point where I'm interested in increasing my accuracy (shooting at NRA Distinguished Expert Light Rifle, 196+/200 but want to do better). I'm curious how the barrel crown affects accuracy from shot to shot. It seems to me that whatever the crown looks like, it looks the same to each slug leaving the barrel, so the effect should wash out once the gun is sighted in. Am I making any sense with this question?
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Old 01-08-2020, 10:19 AM
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Originally Posted by Steeveedee View Post
It seems to me that whatever the crown looks like, it looks the same to each slug leaving the barrel, so the effect should wash out once the gun is sighted in.
One would/might think so but its not, according to those who know much more about physics than I.
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Old 01-08-2020, 10:33 AM
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Quote:
Originally Posted by Steeveedee View Post
I've seen a lot of discussion about barrel crown affecting accuracy. I've been shooting for a number of years, but have only recently gotten to a point where I'm interested in increasing my accuracy (shooting at NRA Distinguished Expert Light Rifle, 196+/200 but want to do better). I'm curious how the barrel crown affects accuracy from shot to shot. It seems to me that whatever the crown looks like, it looks the same to each slug leaving the barrel, so the effect should wash out once the gun is sighted in. Am I making any sense with this question?
l,m going to fellow this, good question.
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  #4  
Old 01-08-2020, 10:41 AM
ammohog
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Interesting crown thread here:

https://www.rimfirecentral.com/forum....php?t=1157477
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Old 01-08-2020, 11:37 AM
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Then there is the mystery of the threaded barrel. And does it shoot better with or with out the thread protector? They really have no crown to speak of .
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Old 01-08-2020, 02:08 PM
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Originally Posted by Al the Infidel View Post
One would/might think so but its not, according to those who know much more about physics than I.
Well, much to my chagrin, I have this question in spite of holding a B. Sc. in physics! I started back in shooting on a more regular basis since retirement, I'm still learning things.

Last edited by Steeveedee; 01-08-2020 at 02:13 PM.
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Old 01-08-2020, 02:23 PM
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I'm not a crown expert by any stretch, but it seems to me that propulsion gasses would push the tail of the exiting bullet unevenly if the crown is not even. That would induce a wobble in the bullet as it gets past the range of those gasses.

I would think a wobble would have minimum shot-to-shot effect if the bullets were traveling in a vacuum or a truly still and homogenous gas. But air has variations and movements that will make a wobble take off high one time and low the next. There's just no telling which way it will drift.

What I do know about crowns is the star pattern spreading out from the rifling will be very even if the bullets are being launched consistently. I had a barrel that the chamber had been cut at an angle relative to the bore. Very inaccurate and the star pattern on the muzzle was very uneven. The new barrel that replaced it is very accurate and the star pattern looks "pretty".
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Old 01-08-2020, 03:12 PM
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The shot-to-shot comparison is what I was thinking. It shouldn't change the trajectory that much. Whatever shape the crown is, it would be constant. Obviously there are other factors in play. Time to go to school on guns, I guess.
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Old 01-08-2020, 04:24 PM
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Given a choice, which crown would you rather shoot? My Kimber 82G:
Before:

After:
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Old 01-09-2020, 11:04 AM
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I guess I'm going to have to go to school on this. Does anyone have a recommendation on some written material that is definitive and factual? I'd rather read a text book than watch you tube videos, personally.

Edit to add- I'm talking about the mechanics of accuracy as a whole subject, not just about the crown.

Last edited by Steeveedee; 01-09-2020 at 11:24 AM.
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Old 01-09-2020, 12:53 PM
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Tips for Accuracy

There is an article "Trouble Shooting Rifle Accuracy" that appeared August 2017 in the magazine American Rifleman. It is from a book by Craig Boddington. The article mainly covers center fire, but just need to substitute "rimfire brands / types" of ammo for hand loading / factory loads. The article covers a great deal, and the book covers stocks, bedding, break in, scopes, different sights, rings, crown, barrel shims, hunting, benchrest, looking in the mirror, trigger pull, etc. It is a good read and very informative. Hope this helps. I am no way affiliated with any of the following, just trying to help in your quest for accuracy:

https://shop.craigboddington.com/pro...e-and-rifleman

Also here at RFC there are stickys about benchrest setup that will help your accuracy / score:

https://www.rimfirecentral.com/forum...d.php?t=582042

https://www.rimfirecentral.com/forum...d.php?t=582312

Here is a link for cleaning rimfire and includes different disciplines of shooting:

http://www.ssvtexel.nl/index.cfm?act...F5CF897974784F

Last edited by ammohog; 01-09-2020 at 01:17 PM. Reason: got it!
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Old 01-09-2020, 06:33 PM
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Quote:
Originally Posted by ammohog View Post
There is an article "Trouble Shooting Rifle Accuracy" that appeared August 2017 in the magazine American Rifleman. It is from a book by Craig Boddington. The article mainly covers center fire, but just need to substitute "rimfire brands / types" of ammo for hand loading / factory loads. The article covers a great deal, and the book covers stocks, bedding, break in, scopes, different sights, rings, crown, barrel shims, hunting, benchrest, looking in the mirror, trigger pull, etc. It is a good read and very informative. Hope this helps. I am no way affiliated with any of the following, just trying to help in your quest for accuracy:

https://shop.craigboddington.com/pro...e-and-rifleman

Also here at RFC there are stickys about benchrest setup that will help your accuracy / score:

https://www.rimfirecentral.com/forum...d.php?t=582042

https://www.rimfirecentral.com/forum...d.php?t=582312

Here is a link for cleaning rimfire and includes different disciplines of shooting:

http://www.ssvtexel.nl/index.cfm?act...F5CF897974784F
Thank You very much! Looks like I've some reading to do.
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Old 01-09-2020, 11:20 PM
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I've always heard and agree with the fact that how the crown is cut isn't as important as how well it is cut. Doesn't matter if it is a recessed, flat, or 11 degree crown, the important thing is it must be cut as centered on the bore as possible so each point of the bore riflings releases at the same time. This obviously means it needs to be cut on a good lathe and indicated on the bore with a good guide rod, not on the outside of the barrel, which may or may not be concentric to the bore.

You hear lots of suggestions to use a brass screw head to clean up the burr at the end corner of the bore at the crown junction but I'm not sure if this is a waste of time or not. More important in my thought is to make sure to cut the crown originally with a good sharp cutter and then check closely for small burrs.

I am kind of hit and miss with the background for rimfire accuracy but I've studied a bit and it sometimes comes out seeming like dark magic or wizardry, but it seems a good barrel installation with a quality barrel is the basis for most of the best rimfire accuracy. Good triggers, solid bolts , and very true actions seem to be secondary and on down the list...

Looking forward to watching this thread to see what tricks a hobbyist target shooter can learn from this group...

Bob
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Old 01-09-2020, 11:37 PM
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how the crown is cut isn't as important as how well it is cut. Doesn't matter if it is a recessed, flat, or 11 degree crown
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Old 01-14-2020, 09:12 AM
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The "after" crown.

Rick H.
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