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Curious
07-18-2016, 04:15 AM
Can anyone tell me the origin of this and if there is any really significance to the 11 degree angle that a target crown is typically cut to?

I guess we could crown a muzzle anywhere from square in over. Im not really convinced that pushing the crown in by 11 degrees plays much of a part in protecting the crown so why exactly do we do it?

Ive seen some guys cut a mini 45 degree crown after the initial 11 degree face and they say they get just as goo a result. Ive only ever done 11 degree ones but is there only one way to skin this cat?

Rubicon Prec.
07-18-2016, 10:21 AM
I believe it was the army testing years ago where the 11 degree crown came from. I am a bit suspicious of a blanket assumption that one angle will be the most accurate for every rifle and every load.

On a threaded muzzle where there isn't much real estate, I do do a 169 degree included angle to give some protection when there is no muzzle device on. I break the edge of the bore to 60 degree included angle.

http://img.photobucket.com/albums/v654/300sniper/rifle%20tools/10E9392B-0960-431B-8E49-ECBA001627BA_zpststliif9.jpg (http://smg.photobucket.com/user/300sniper/media/rifle%20tools/10E9392B-0960-431B-8E49-ECBA001627BA_zpststliif9.jpg.html)

On a field/target rifle, I do a 60 degree included angle break at the bore then a section perpendicular to the bore then a 90 degree included angle step out .090" deep. I don't do benchrest rifles but I suspect I would use this muzzle style with a much shallower recess.

http://img.photobucket.com/albums/v654/300sniper/rifle%20tools/FD6C4500-5518-4D9D-87BC-03E8418F0F7C_zpsrr3peueq.jpg (http://smg.photobucket.com/user/300sniper/media/rifle%20tools/FD6C4500-5518-4D9D-87BC-03E8418F0F7C_zpsrr3peueq.jpg.html)

Hippy
07-20-2016, 05:24 PM
I was in the belief that the 11 Degree crown helped guide the brush bac into the bore.

Since we what are talking barrel crowns what is a "Floor Board and Step Crown" ?


Jim

Mike Bryant
07-20-2016, 10:59 PM
Red Cornelison told me that he came up with the 11 degree crown. I wouldn't be surprised if that was so. 11 degrees was picked as that was supposed to be the angle that gas exited the bore when the bullet cleared the bore. Red was pretty innovative in his time. He was pulling .22 LR bullets and necking the pulled cases down to .17 long before the factory came out with the .17 rimfires. I haven't seen that the crown shape makes much difference in accuracy as long as it is burr free and is cut clean. I've used the 11 degree crown for years with a 60 degree bevel cut at the bore as well. It shoots well and seems to last longer than the current popular squared off crown, IMO.

A step crown is what is shown above in the second photo. A floorboard crown would be a crown for protecting a rifles crown while carrying it muzzle down against the floorboard of a pickup. I've used a 30 degree crown for that very reason. It makes a very deep recessed crown that protects the bore and allows the rifle to be abused by carrying it muzzle down against the floorboard of a pickup.

skeetlee
07-21-2016, 04:08 PM
A little off topic and I have mentioned this before. With me having a 300 yard range directly behind my machine shop I've been know to do some crazy testing. One Sunday afternoon when I had nothing better to do, I did some testing with different types of crowns and with different methods of dialing in. I even did a crown with no dialing in. I just chucked the said barrel up in my three jaw and made a cut.
My test barrel was a ppc barrel that had a couple matches on it, if memory serves me correctly. The barrel was still a solid shooter, that much I do remember. Anyway to make a long story short, I found no difference in crown shape, and even with the faced off three jaw crown, the barrel still grouped well. Actually I saw no difference in my groups what so ever.
This was one afternoon, with just a couple 3 or 4 shot groups shot with each example. I wouldn't call what I did a real in depth test, but what I did clearly see was pretty surprising. I wouldn't ever encourage anyone to cut a barrel crown in a three jaw with no indicating of course!! The barrel did shoot though.
I wish I had done an 11 degree crown in the three jaw, but I didn't think of it at the time. If I ever get caught up in the shop maybe ill give that a try?? Lee

blades
07-21-2016, 04:32 PM
In books I have read crown style has little or no importance as to effect on projectile but a countersunk crown does provide some degree of protection to the critical edge of the bore/rifling. No it is not to guide the bore brush back in- if you want your crown to last you do not pull said brush back through- fastest way I know of destroying a shooter. On my match rifles and pistols over the years I have had just about every description on the end of the barrel ( flat, concave , convex)- never could tell any difference over many thousands of rounds fired in many disciplines. But I can tell you that if it isn't square to the bore all bets are off and of course no burrs. ( well with single projectiles at any rate- done some pretty redneck deals with shotguns but that's another ball of wax) ( made a couple rabbit hat tricks work out pretty well on muzzeloaders as well)

Mike Bryant
07-21-2016, 10:56 PM
I've heard of pushing the brush through the muzzle and then taking it off before pulling the rod back through the barrel, but I've never seen it done at a benchrest match.

Wayne Shaw
07-22-2016, 06:03 AM
You would wear a path from the front to back of your cleaning table taking a brush on and off so many times.

Butch Lambert
07-23-2016, 07:38 PM
Mike I still have some of Red Cornelison's necked down 22RF mag brass and some with the 17cal bullets. He shot them long before the 17HMR was introduced. I use a 90deg crown on my BR rifles.

Jay Cutright
07-25-2016, 09:40 PM
You would wear a path from the front to back of your cleaning table taking a brush on and off so many times.

Drill out the female thread on your cleaning rod just enough to clear the threads so you can set a catch pan under the muzzle and push a dozen brushes through and each one will fall off on the back stroke and land in the pan. Thought about this many times and decided I should avoid anything that might make me hate shooting.
I clean less all the time now.😕

R.G. Robinett
07-25-2016, 10:00 PM
Drill out the female thread on your cleaning rod just enough to clear the threads so you can set a catch pan under the muzzle and push a dozen brushes through and each one will fall off on the back stroke and land in the pan. Thought about this many times and decided I should avoid anything that might make me hate shooting.
I clean less all the time now.😕

:)

Wayne Shaw
07-26-2016, 06:18 AM
Drill out the female thread on your cleaning rod just enough to clear the threads so you can set a catch pan under the muzzle and push a dozen brushes through and each one will fall off on the back stroke and land in the pan. Thought about this many times and decided I should avoid anything that might make me hate shooting.
I clean less all the time now.😕

Now why didn't I think of that? You still have to go get them to clean the ammonia/solvent off but one trip is better than 12!

skeetlee
07-26-2016, 04:34 PM
Ive done what Jay just described. I drop my brushes in to a pan of alcohol though. lee