Crown preference

[Rick in Oregon]

Was there any data on what the difference was between a recessed and 11 degree crown?

It's common to do a 11 degree muzzle crown and recess it with the 'ridge' of the recessed part protecting the crown, sometimes called a 'floorboard' crown for resting the muzzle on the truck floorboard/firewall and still retain the 11* crown.

There was much lab data using high speed cameras to show the sonic wave ahead of the bullet, along with the disturbed trail behind the bullet with and without the 11* crown. From the labratory photos in PS, it was apparant that the 11* crown created the very least disturbance to the heel of the bullet.

 

[jwv2001]

All About Rifle Muzzles and Crowns

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This might help?

Mike, Thanks for the article. I hope shooters understand what and where the crown is. I hope they understand whatever design that is on the end of the barrel is not the crown. 11 deg,, target, recessed, are all terms that confuse the issue. Hyperbole. If they still don't understand, they have to read that article again.

 

[jackieschmidt]

Years ago, Gene Bukys and I did a test on this very subject, using a Light Varmint Benchrest Rifle. We would fire some groups, take the barrel off and to my shop, We tried a simple flat crown, a recessed crown, and a 11 degree. The bullets were Bruno OO 68 grn boat tails.

We could not determine any difference in the accuracy potential of the rifle with any one of the three.

I prefer a countetbored recess crown because it looks good.

 

[V35]

I usually cut a flat recessed, sometimes I do the 11 degree, well close to that, I just use the marks on the compound. I trigged them in forever, then realized I would never see the difference. However, If someone requested an exact degree crown I would do it for them. On my personal rifles I always shoot supressed, so the whole gas movement theory is totally out the window at that point.

 

[JMayo]

I run Ezell tuners on my short range (11 °).
They cover up all but the center much like jackie's counter bore
A friend has a big barrel counter bored 1.5 -2" down the muzzle. Almost like a built on bloop tube on his hvy 6ppc. No adjustable tuner.
Interesting idea to me.

 

[jelenko]

We could not determine any difference in the accuracy potential of the rifle with any one of the three.

Thank you!
This was the point I was trying to get at when asking about data.

 

[ELR LVR]

Curious as to why this would be true. I've had 3 long range benchrest barrels that were square cut and flat crown. I always thought I had to be a little bit more careful with them

In order to do 11 degree, the bore must be dialed in concentric as perfectly possible to the bore centerline
otherwise the crown will be offset
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Flat, it would not matter if the barrel was out of concentricity a few though
I have found a few factory remmy barrels with their factory rounded type crowns obviously out of concentricity when dialed in on the lathe though.
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The crown has to do with how the high velocity gases escape the bore behind the bullet and affect the base of the bullet.
(Supposedly from what I heard 30 some years ago, some NASA JET Scientist Engineers or some such people..... found 11 degree is the sharpest angle the gases will still follow the surface with laminar flow, thus pulling the gases away from the base of the bullet the quickest.
Now this may or may not, be relevant to rifles and may depend mostly on the velocity of the gases
Such as maybe it comes into play more with a 220 swift than it does with a .223
Or It may only be relevant to the velocity of escape gases with a Space Shuttle and the info got transferred over to us and we adopted it just for "Feel Good" precautions, got experimented with, found no big advantage to our purposes, but still got practiced and continually requested so it became
"A thing"
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If the gases favor one side, it will push the bullet off to one side upsetting its flight pattern.
(How much would obviously depend on how much out of concentricity the barrel was)
I have not.... nor do I care to test this, (Unless someone is willing to contribute all the necessary components) lol
All I know is, Flat is just as accurate as 11 degree and flat is an easier operation to ensure.
I do not like however, someone taking a 60 or 90 deg countersink to break the edge of the newly cut bore since this obviously now presents a 60 or 90 degree crown.
I do not take a countersink to a newly cut bore and all my rifles are more accurate after removing such a countersunk bore with either flat or 11 deg, or even ..........ready? even a 12 degree crown
and no countersink on the muzzle (this to me is a shortcut some people like to take to touch up a crown)
Fine for them, not for me

 

[284winner]

Barrel crowns

 

[Will Henry]

A few years back (about 45 of them) a Winchester rep showed me some records kept by some of the Winchester techs who were testing crowns. They arrived at the conclusion that the best crown was a flat crown which was recessed. The recess was two calibers in diameter and two calibers deep. In other words, a 308 would have a recess approximately .600x.600. I saw some Winchester Palma rifles which were crowned this way. The truth is, unless your rifle/cartridge/ shooter combination is potentially capable of .125 moa, you will never be able to tell. I doubt that any particular crown, as long as all are perpendicular to the bore, will turn a .5 rifle into a .250 rifle, and certainly not a .125 rifle. WH

 

[Alex Wheeler]

In my opinion theres no difference in accuracy.