Crowning A Barrel

[ChemDave]

What is the purpose of crowning the end of the barrel. Is this a cosmetic thing or does it affect the ballistics in any way? Is there any advantage to getting a barrel crowned when it is just plain?

Thanks

[Brick]

Crowning a barrel smooths the rough edges from forging and cutting the rifling. There are different shaped crowns but all are for the same purpose. Leaving the barrel rough or damaging the crown would result in poor accuracy.

[Delkal]

A proper crown is important in rifles if you want to shoot under an inch at 100 yards. It is less important in a pistol (unless its a Contender/ Encore/ or other long range pistol).

Basically....If the crown is not perfect gasses from the rough / uneven parts will nudge the bullet in a random direction.

[harold63]

Basically....If the crown is not perfect gasses from the rough / uneven parts will nudge the bullet in a random direction.

Pretty much.

A perfectly cut crown may not give better accuracy on a pistol just because the end of the barrel was already straight. Crowning may straighten an otherwise not so perfect end and help accuracy, but it would show up until you're in stratosphere distances for a pistol. What will happen on a crown that isn't cut perfectly is bullets being pushed from the uneven part in relation to the charge in the cartridge. For example, a crown cut correctly will push gases straight, but at an even pressure all the way around, and the clincher is it's being pushed forward. Small charge or heavy charge will push the bullet straight and you see the charge variance in total distance and bullet drop.

If a crown is cut off center just a bit, the charge will push the bullet opposite of where it is off center. If you're shooting factory ammo that has slight variances in the charge, this can actually make the accuracy worse because the bullet is being pushed away from the direction you're aiming. A heavier charge may make the POI 3" high and right where a cooler charge may only make the POI 2" high and right. The gas is pushing against the bullet off of the off center bevel. A straight crown or a 'factory' crown won't do this if the barrel is cut straight, and that is rare that it isn't, even with a HIPOINT.

If you need every bit of accuracy for something like slow fire, then it is worth it along with your other accurizing goodies, but the crown has to be perfectly cut to see any improvement, and you'll not likely see anything at a 7 to 10 yd distance.

[harold63]

You can crown this barrel 'till the cows come home and it isn't going to shoot any better.

http://www.glocktalk.com/forums/show....php?t=1553087

[Delkal]

You can crown this barrel 'till the cows come home and it isn't going to shoot any better.

Totally agree with ANY handgun shot at less than 25-50 yards. I did have one rifle and some contender barrels that did benefit from a proper crowning. They all improved some and in one case my groups went from ~1.5 inches to a little under 1 inch at 100 yards.

In that case it was worth it but shooting a handgun at 30 feet the theoretical increase in accuracy would be under 0.05 of an inch. You wouldn't even notice it. There are many better ways to increase accuracy with a handgun.

[JenniferG]

You can crown this barrel 'till the cows come home and it isn't going to shoot any better.

http://www.glocktalk.com/forums/show....php?t=1553087

After reading through that on the Glock forum I'm appreciating my Poofa pals even more. That gun can be repaired or replaced. The commenters well, lets just say "Hokey Smokes"!

[Im not Batman]

To understand Crowning of a barrel, one has to understand " surface tension ".

As stated in other replies, it's how the gasses push the bullet off course.

As the bullet leaves the barrel... There is a moment where the gasses envelope the round.. Talking millionths of a second here.

As the bullet leaves the barrel, the gasses behind it start to expand in all directions ( MUZZLE FLASH ) and this is where "SURFACE TENSION" comes into play.

Gas...like water and electricity and power are LAZY and take the easiest and shortest way out. So, say you have a noticeable "NICK" on the muzzle ..

This creates a small VORTEX at that spot and draws gasses to it creating a asymmetrical ( un- even ) force on and AROUND the bullet..if just for a quarter of a second...it is enough to start a wobble in the spin.

Go get a plastic (new...good condition) plastic cup... We ALL KNOW how to heap water in a cup... Now take a knife and nick it...heap the water again and watch the "nick"

Now bevel the inside edge to rmove the nick and try it again.

Crowning a barrel... Just short of rocket science.
Plenty of super slow mo bullet video on the YouTube will give you a good idea of what happens.

This is the best video I can find.
As you see, there is gas leaving the muzzle BEFORE the bullet....

Crowning the barrel?? Hey....auto racers have done LESS just for a 1/10 of a second gain

http://www.youtube.com/watch?v=otpFN...e_gdata_player

[Im not Batman]

After reading through that on the Glock forum I'm appreciating my Poofa pals even more. That gun can be repaired or replaced. The commenters well, lets just say "Hokey Smokes"!

Wow...sad quality there. Scary too

Have to wonder how thin it is at the headspace??

[mauser]

What is the purpose of crowning the end of the barrel. Is this a cosmetic thing or does it affect the ballistics in any way? Is there any advantage to getting a barrel crowned when it is just plain?

Thanks

The "crown" is the edge of the opening of the bore or the profile of the muzzle end of the barrel.

To recrown it is to recut it to improve the quality of the cut.
Crown is a noun, refering to the end of the barrel.
Crown is also used as a verb meaning to make a cut to refresh or reshape the actual crown.
A perfectly smooth and even cut is the desired condition of the muzzle end, (crown), of your barrel.
It isn't going to make a difference in ballistics if you're referring ballistics as muzzle velocity and muzzle energy, that's determined by bullet weight, size, shape, and fit in the barrel, barrel length, and the type and amount of propellant, (powder and primer combination). It isn't quite that simple, but that sort of covers the basics.
If you're thinking of ballistics as the performance of the projectile after it leaves the barrel, in terms of accuracy, you may notice a difference with recrowning if the original crown was damaged or of poor quality. If the crown is severely damaged, heavily worn or of very poor quality you will probably notice a marked improvement. Short distance, as in self defense pistol distance/range probably won't show much if any difference unless the damage/wear/quality is extremely bad.
As has already been stated, crowning evens out the muzzle to allow the gasses pushing the bullet to escape the barrel more evenly. If a straight cut barrel is perfectly cut and the gasses escape evenly around the bullet, that's as good as it's going to get. If there is any imperfection in the cut and the gasses escape unevenly it will have a direct affect on accuracy, and recrowning, (if done properly) should correct the imperfection(s) and improve accuracy. The "profile" of the "crown" is to protect the true crown, or the end of the bore. You'll notice that most crowns are recessed in some way;



But not these two:


Some are slight, some are extreme, some are not recessed at all.
Those that are straight leave the crown more susceptible to damage.
Whether radiused, straight cut with a recess or rebate, or counterbored, the intention is to have the opening of the bore slightly behind the absolute end of the barrel to protect the critical edge of that all important hole in the middle. Any metal protruding beyond the center hole will help to protect the edge of the bore, and that's where the bullet has it's last contact, therefore making it critical that that contact be as even and perfect as possible for best accuracy.
(Ever bump the end of your barrel on anything? A recessed crown helps to keep that unintentional contact from being on that critical edge.)
You can defeat the purpose of the recessed crown by cleaning your gun from the muzzle end, especially with a steel cleaning rod. Just rub one side with the cleaning rod while pushing in and out and the abrasion can cause uneven wear on the crown. Brass cleaning rods are better than steel and aluminum is better than brass, but cleaning from the breech end is best if possible.