Cutting muzzle Crown and Chamfering Chambers

[Carry_Up]

I have used the piloted Brownells 45 degree chamfering tools on revolver chambers, and for smoothing up the barrel crowns. It is too bad that the fit of the ejector star on GP and SP models is so terrible, because you could otherwise chamfer the entire chamber mouth, instead of only part of it. Even so, the chamfer does help when inserting the round into the chamber.

On a number of GP and SP models I have found that the factory "crown" is not ground on center with the barrel axis. That means that no pilot was used to form the crown and it is there purely for looks. Using the piloted 45 degree tool, there is usually up to 120 degrees of the existing factory crown left untouched by a considerable amount of cutting. Going deeper would eventually make an even crown, but it looks like about .100 of metal removal might be necessary. I suppose cleaning up 2/3 of the crown might help accuracy a bit, but it falls short of the whole purpose of cutting a crown in the first place. Just something to consider.

Carry_up

 

[woodsy]

Are you a gunsmith?

 

[I_Like_Pie]

I too have re-cut the crowns on my GP and SP guns. They just didn't seem right to me for some reason. I worked mine like you with a 45 tool from brownells and them used a ball bearing and valve grinding compound.

Of course I couldn't tell if it shot any better, but the piece of mind (and a rainy day) fixed the problems that you also had.

 

[Carry_Up]

I have confirmed the same lack of alignment between bore axis and factory crown on at least 10 DA revolvers. The chambers are aligned with the cylinder face - but that would be an absolute minimum requirement for any revolver. How hard would it be to produce a beautiful cylinder with a fitted star? That's the whole gun. Instead you get this wimpy star that wobbles around and isn't even flush with the cylinder face.

A correctly cut crown increases accuracy by insuring that the escaping gasses do not push the bullet one way or the other as the bullet exits the muzzle. For those who haven't already thought of it, using a ball bearing to make a crown is a waste of time unless you are concerned about cosmetic appearances only. The crown MUST be aligned concentric to the barrel bore axis, and this alignment can ONLY be done with a piloted tool. The bearing will eventually produce a smooth crown, but at some unknown incorrect axis relative to the bore. Smooth or not, the accuracy of that barrel will not be improved by this work.

Since we have to re-cut the crown anyway, the factory would be doing its customers a favor by leaving the muzzle alone rather than grinding a fake crown onto the end. Or would it be too much to ask for a correctly cut crown in the first place?

-CU

 

[Jimbo357mag]

I have used the piloted Brownells 45 degree chamfering tools on revolver chambers, and for smoothing up the barrel crowns. It is too bad that the fit of the ejector star on GP and SP models is so terrible, because you could otherwise chamfer the entire chamber mouth, instead of only part of it. Even so, the chamfer does help when inserting the round into the chamber.

I always heard that you shouldn't chamfer the ejector star on the cylinder because you need that edge for good cartridge ejection but I can imagine just slightly breaking that sharp edge wouldn't hurt anything and might help with the bullets entering the chambers. :shock: :shock:

 

[Carry_Up]

Yes, the whole point of chamfering the chamber mouth is to break the sharp edge that could catch on a round during loading. A properly done chamfer is not even visible unless you hold it up to a bright light, and it will avoid the same type of interference during case ejection. Since the radius on the factory ejector star is actually larger than the chamber mouth, no chamfering is necessary (or possible). The sloppy fit saves a step or two during assembly, but I can't believe that modern CNC equipment - which everyone claims to use - won't do a better job than this!

-carry_up