How to Crown a Barrel

[doubleboost]

Hi
Lads
I have been asked to "crown" a .22 rifle barrel
What do I need to know
John

[Arbalest]

No idea, hopefully an expert will be along soon. I'd like to know the answer to this as well as I do know it's very important to get it right. What type of rifle is it?

[DaveH]

(06-02-2014, 11:07 AM)doubleboost Wrote: Hi
Lads
I have been asked to "crown" a .22 rifle barrel
What do I need to know
John

It must be absolutely even all the way round, no chatter marks or burs - not even tiny tiny ones.

DaveH

[Highpower]

John, when you set up the barrel in the lathe indicate it off of the bore and not the OD of the barrel. Slip a snug fitting pin (preferably ground) a couple of inches into the muzzle with a bit sticking out to dial it into your 4-jaw chuck. When you are done cutting the new crown, lap the muzzle with a brass 45° "center" and some fine abrasive compound. A brass wood screw with a round head could be substituted for the 45° center/lap. Chuck it in a hand drill, apply the compound, and do small figure 8's on the muzzle while slowing running the drill.

Dave is correct. The ends of the rifling (lands) need to be smooth, even and concentric with the bore. If you are working on a "rounded" style of crown, this is the typical type of grind used on the lathe bit.

[doubleboost]

(06-02-2014, 05:06 PM)Highpower Wrote: John, when you set up the barrel in the lathe indicate it off of the bore and not the OD of the barrel. Slip a snug fitting pin (preferably ground) a couple of inches into the muzzle with a bit sticking out to dial it in your 4-jaw chuck. When you are done cutting the new crown, lap the muzzle with a brass 45&#176: "center" and some fine abrasive compound. A brass wood screw with a round head could be substituted for the 45° center/lap. Chuck it in a hand drill, apply the compound, and do small figure 8's on the muzzle while slowing running the drill.

Dave is correct. The ends of the rifling (lands) need to be smooth, even and concentric with the bore.

What angle do I use or am I just braking the edge
The barrel has been screw cut for a moderator and just faced off
John

[Highpower]

(06-02-2014, 05:14 PM)doubleboost Wrote: What angle do I use or am I just braking the edge
The barrel has been screw cut for a moderator and just faced off
John

In that case it could be used as is (faced off) if they never intend to shoot it without the moderator. Otherwise I would suggest using a standard 11° target crown shown on the right.

[EdK]

What's the purpose of that end treatment?

Ed

[Micktoon]

Just wondering that myself Ed lol

Cheers Mick

[DaveH]

1) It looks nice
2) Stops the end of the bore being damaged by misuse.
And 3) The most important it allows the air (remember for an air rifle) to come out of the end of the barrel evenly. This is really important on an air rifle because the air in the barrel is traveling 4 to 6 times faster than the pellet. So as the pellet leaves the barrel end the air "whacks" the pellet up the backside. If the air comes out skew it will cause the pellet to wobble and lose accuracy.

DaveH

[DaveH]

Bit of reading John - some pics http://www.pyramydair.com/blog/2011/09/t...the-crown/

DaveH