Barrel Crowns

[tonykharper]

Barrel crowns are not often discussed on the forums. Perhaps they aren't important and don't need to be discussed?

But since we cover them up with our tuners and other muzzle devices, I wonder how often they get looked at and checked for damage. After all, that rod and jag get pulled through the crown several times after each target.

There are many ways to cut a crown and I'm sure everyone has their own opinion on what works best, but I would like to show an 11-degree crown that I think works well.



This crown was cut by Mark Penrod, an excellent gunsmith from Indiana. If you look carefully, you will see Mark cut this about as good as one can be cut.

Here is another look at an 11-degree crown (not cut by Mark but still good).



Perhaps crowns aren't that important but one should at least take a look at yours from time to time.

They are one of the things that can be addressed fairly easily.

Please share your thoughts.

TKH (4628)

[Pete Wass]

It is important to have the muzzle running dead straight when cutting the crown and the most important thing is to cut a small radius inside the crown. The radius will deter a lot of potential damage from jags or brushes. I've used a number of different crowns but lately have used simple 90* crowns with a radius cut inside the muzzle.

To that end, years ago, there was an article in Precision shooting magazine in which the author had experimented with crown shapes. As I recall, he cut a barrel that was shooting well off with a hacksaw at an angle and then shot the rifle. The rifle still shot the same as it had before he mangled it and didn't change the way it shot with whatever crown he used. That said, why tempt fate? A lovely polished crown is beautiful to behold.

Pete

[GeneT]

It is important to have the muzzle running dead straight when cutting the crown and the most important thing is to cut a small radius inside the crown. The radius will deter a lot of potential damage from jags or brushes. I've used a number of different crowns but lately have used simple 90* crowns with a radius cut inside the muzzle.

To that end, years ago, there was an article in Precision shooting magazine in which the author had experimented with crown shapes. As I recall, he cut a barrel that was shooting well off with a hacksaw at an angle and then shot the rifle. The rifle still shot the same as it had before he mangled it and didn't change the way it shot with whatever crown he used. That said, why tempt fate? A lovely polished crown is beautiful to behold.

Pete

I'm with ya Pete! I have never seen a good crown create negative consequences. I *have* seen a bad crown open groups up tremendously. I've never tried the hacksaw test myself, but I've seen it reported often enough that I think it's believable. I do, however, think that some luck is involved. There is somewhere along the crown that must matter significantly - perhaps it's only when you get the right burr at 10 & 2 - I really don't know - but I've seen crowns do major damage. One instance was a Ruger 77 in .357 that was poorly crowned - it couldn't shoot less than 10" at 50 yards. I recut the crown and it settled down to ~1.5" (No, still not a shooter, but a tremendous change from just a new crown.) The previous crown had visible machining marks, but wasn't anything near as horrible as a saw-cut crown would be.

I don't think there's any magic in the angles (11* vs anything else), but a chamfer will surely help preserve a crisp edge. That's a long way of saying - I think a bad crown can ruin everything, a good crown preserves, but does not improve, the accuracy of a barrel.

GsT

[tim]

Good topic Tony.
Relative to your last line…..you are one that can re crown in a lathe, but thoughts on refreshing a crown without access to a lathe. i’ve seen, over the years, everything from lapping compound on a brass screw, drill bits, to some version of sandpaper.
Any thoughts ?
Lastly, do you believe a crown needs attention after some time or simply inspected ?

[GeneT]

Good topic Tony.
Relative to your last line…..you are one that can re crown in a lathe, but thoughts on refreshing a crown without access to a lathe. i’ve seen, over the years, everything from lapping compound on a brass screw, drill bits, to some version of sandpaper.
Any thoughts ?
Lastly, do you believe a crown needs attention after some time or simply inspected ?

...but I'll interject anyway.

I've seen some pretty nice crowns done with brass screws and Clover compound - that's definitely a step above may crowns, and an abrasive compound is not going to leave a noticeable burr - so as long as the cut is straight, I think it's a good way to go.*

The best inspection for a crown (and the rest of the system) is to shoot a group. Never lose track of the goal. If your rifle has a huge ding in the crown and shoots screamers - well, take good care of that ding!

* For many years telescope lenses were ground, by hand, walking around the stand for the lens, scrubbing in a pattern. Don't tell me you can't get a good crown by hand. I prefer to cut mine in a lathe, for convenience, but saying it can't be done by hand is nonsense.

GsT

[tonykharper]

Good topic Tony.
Relative to your last line…..you are one that can re crown in a lathe, but thoughts on refreshing a crown without access to a lathe. i’ve seen, over the years, everything from lapping compound on a brass screw, drill bits, to some version of sandpaper.
Any thoughts ?
Lastly, do you believe a crown needs attention after some time or simply inspected ?

I agree with GsT. I've seen some really nice crowns done with hand tools. I've always been against the type that have a pilot that goes up inside the barrel and you turn the cutter by hand.

But I've seen at least one really good shooter use one and it didn't seem to hurt his scores.

K.C. Young of Black Creek Va. had a rifle that had a big chunk out of the barrel right at the corner of the crown. He showed it to everyone and asked do you think I need to fix this thing?

He was beating us with it as it was, so we told him no, and I don't think he ever recut the crown.

That said, I just can't do that. I would have had to recut it. Another look at what I think to be a pretty 11-degree crown.



TKH (4628)

[tim]

Why against the piloted ones? I’ve seen a few but I’m guessing you may have not ever seen one by Ross Sherman who was with Ed Shilen up here before he went to Texas. A beautiful 7 flute affair with long properly fit pilots. Guy was a master machinist.
For the non-lathe guys, any thoughts?

[Dennis D.]

I don't think that is an 11 degree crown. If you take a close look it appears that there is a chamfer at the bore, my guess is either 45 or 60 degrees. A true 11 degree crown would have no chamfer at all.

Dennis

[tonykharper]

Why against the piloted ones? I’ve seen a few but I’m guessing you may have not ever seen one by Ross Sherman who was with Ed Shilen up here before he went to Texas. A beautiful 7 flute affair with long properly fit pilots. Guy was a master machinist.
For the non-lathe guys, any thoughts?

Tim,

You are right, I haven't seen the tool made by Ross Sherman but I do have one made by Pacific Tool and Gauge. My tool uses the same pilots that their chamber reamers use.

When I bought it, I thought I would use it but decided not to. My fears are probably unreasonable. I also never use Deltronic pins to measure bore size.

Pushing these items into the lands may never hurt a thing but I have decided not to do it. Yes, I do use pilots on chamber reamers only because I can't figure out how not to.

I'm a strong supporter of post chamber lapping. That cleans up anything in the bore that I may have upset while threading, chambering, finishing the chamber, or crowning.

Looking at the pic I can see where that crown appears to be greater than 11 degrees. I would never take bets that it is exactly 11 degrees, but I'm sure it isn't anywhere near 45 or 60.

Please share any methods you use to crown your barrels.

TKH (4628)

[tonykharper]

I don't think that is an 11 degree crown. If you take a close look it appears that there is a chamfer at the bore, my guess is either 45 or 60 degrees. A true 11 degree crown would have no chamfer at all.

Dennis

Dennis,

Which chamfer are you referring to? If it is the one in the barrel bore, I would suggest you always break that edge. A sharp edge can be damaged easily.

TKH (4628)

[tim]

Tim,

You are right, I haven't seen the tool made by Ross Sherman but I do have one made by Pacific Tool and Gauge. My tool uses the same pilots that their chamber reamers use.

When I bought it, I thought I would use it but decided not to. My fears are probably unreasonable. I also never use Deltronic pins to measure bore size.

Pushing these items into the lands may never hurt a thing but I have decided not to do it. Yes, I do use pilots on chamber reamers only because I can't figure out how not to.

I'm a strong supporter of post chamber lapping. That cleans up anything in the bore that I may have upset while threading, chambering, finishing the chamber, or crowning.

Looking at the pic I can see where that crown appears to be greater than 11 degrees. I would never take bets that it is exactly 11 degrees, but I'm sure it isn't anywhere near 45 or 60.

Please share any methods you use to crown your barrels.

TKH (4628)

Never crowned one but have used the Sherman tool on rare occasion with RF, mostly with 6mm ‘s. It uses pilots that are longer than typical reamer pilots and a few additional ones I had made for various 22 diameters. He was a master at sharpening the cutters and made very few sets, was lucky to score one. I ‘ve been blessed, however, largely avoiding cleaning damage( that I know of ).

[Dennis D.]

I do break the edge of my crowns but doing so turns the crown into whatever angle you use on the break. personally I use 45 degrees just enough to clean up to the groove. Doesn't matter how small the break may be the last thing the bullet sees is the break angle. For rimfire I believe it's good because our barrels last for a long time so they see lots of cleaning, also it pulls material away from the bore if you use a lathe bit to do it. In theory you could back bore it that way as far back as you like but it would just make it hard to clean the muzzle with no side benefit that I can see.

Dennis

[kevinnevius]

All:

I have never been a fan of putting anything in the muzzle (even a live pilot). Some of the MI lands offer so little contact for a pilot that I am always worried about marring them. The bullet transition in this area is critical to overall accuracy IMHO.

I have machined and used small chamfers in my crowns, mostly because I thought it would take cleaning abuse throughout the life of the barrel better, but went away from that also. If you consider it geometrically, any misalignment or minute error in concentricity produces an elliptical edge. Because of that, I have used only offset square cut crowns. Nothing goes into the barrel, and after I indicate in the bore nothing to me is as error free a transition.

So, I turn for ID to OD concentricity first, then cut as clean a crown as I can - which is very dependent on cutting material / speeds / feeds and lubricant. I use a TIN coated Kennametal insert, in a Dorian positive rake tool holder. I crown at 540RPM, wet with Tap Magic fluid. Not sure if that's optimum, but it has worked well for me in the past.

The picture is a crown finished last weekend.

All the very best,

kev

[tim]

Good point Kev, I have never used my tool on MI barrels.
I have had made up different pilots for various 22bore sizes in brass. typically they go in lubed as is the cutter.
Curious now to see how/if they fit.

[tonykharper]

One of the reasons I started this thread was to show off Mark Penrod's workmanship on a pic of a crown he sent me.

Somehow in my feeble mind I confused Mark Penrod"s name with Brian Voelker. The only thing they have in common is they are both excellent gunsmiths.

Mark, please accept my apology.

Brian I'm sorry to have used your name incorrectly.

I'll go sit in the corner for a while.

TKH (4628)