Degree of Camfer on 90 Muzzle Crown

[58weasel]

I note that often a 45 degree camfer is used on the lands & grooves as a final touch to the muzzle crowning operation.
This, I suppose, gives a little insurance when a bush is pulled back through the muzzle when cleaning, among other unknown advantages.
I note that my 20" Krieger DCM uses a 45 degree camfer; whereas David Tubb apparently uses a 30 degree camfer.
Is one better than the other?
Is using a reamer better than simply using a lathe for that final touch?
Thanks in advance for sharing your experience and practice!

 

[Preacher]

I don't put a camfer on the crown, I just cut a 90 degree angle at a fast speed and slow cuts, with a newly sharpened cutter, in the lathe...
They all have shot just fine..
I do not ever pull a brush back through a bore, I remove it every time.
It's a PITA but the results are there..

 

[58weasel]

Appreciate the insight, Preacher. Based on what I've read on 6mmbr.com, I have ceases to pull a brush back through my barrels; though I continue to do so with a patch.
The rifle will eventually belong to one of my "heirs or assigns" and they might not be so fastidious.
PT&G make a piloted reamer that cuts the 30-degree camfer, and I suppose one for 45-degree would be available too.
So, the barrel will be camfered for posterity's sake, and is not a bad idea on a field rifle in general.
Just not sure whether to get 30 or 45.

 

[Preacher]

Bad spelling is all, chamfer is the correct word...

 

[Scott Harris]

I put a 45 deg chamfer, primarily to protect the crown from cleaning rods pulled back through. it works well with zero adverse effect on accuracy....in fact, it enhances it by protecting the crown I dont think the angle makes a bit of difference as long as it is uniform. I use a hss indexable boring bar from warner that works well

 

[58weasel]

Thanks for the spurrlin correction. They threw me out of the 3rd grade as a hopeless scholar.
Nothin' else to do 'cept rifle shoot after that.
Deprived childhood.

 

[WayneShaw]

When you are at a match with just two relays, you are hard pressed to get back, clean your gun, reload, finish cleaning, in time to get back to the line on time. I have never seen a shooter, take a brush off, pull the rod back and put the brush back on, at a benchrest match.

If you are shooting at home, go for it.

 

[butchlambert]

When you are at a match with just two relays, you are hard pressed to get back, clean your gun, reload, finish cleaning, in time to get back to the line on time. I have never seen a shooter, take a brush off, pull the rod back and put the brush back on, at a benchrest match.

If you are shooting at home, go for it.

You are correct Wayne. Too much club shooting range advise going on here.

 

[Nomad47]

Well, if Preacher says that's the way he does it, it is good enough for me.

 

[JRS]

Why not Donovan?
I watched a very informative show put on by the McMillans when living in Phoenix years ago. They had a 250x B&L microscope set up for anyone interested to observe the crown on one of their barrels. After wearing out numerous brushes during the course of a few hours, the barrels crown showed ZERO damage. That barrel steel is MUCH harder than a bronze brush

 

[Preacher]

Water will wear a groove in stone if done often enough !!!!!!

 

[butchlambert]

Need to go to another thread. People have their reasons both ways and won't change their minds. I think you are wasting bandwidth posting an opinion on this, right or wrong.

 

[Jay Christopherson]

Water will wear a groove in stone if done often enough !!!!!!

Yep... and it only takes a few million years or so, give or take a couple hundreds of thousands...

I have a lot of respect for Preacher's opinions, but I've pulled a lot of brushes back through the barrel and have not seen the slightest bit of damage done to the crown, observed via microscope (NOT borescope).

EDIT: I should mention that I only run my brush through maybe half a dozen strokes every 100 rounds or so, if that. BR shooters probably do something like 60X that, so TMMV.

 

[JRS]

Water will wear a groove in stone if done often enough !!!!!!

Yep... and it only takes a few million years or so, give or take a couple hundreds of thousands...

I have a lot of respect for Preacher's opinions, but I've pulled a lot of brushes back through the barrel and have not seen the slightest bit of damage done to the crown, observed via microscope (NOT borescope).

+1

 

[58weasel]

Donovan:
Appreciate the BR info. I know they even make a tool to reface your crown in the field. So that straight pristine 90-degree crown is indubitably the best, but in the rough and tumble field may be a bit vulnerable. The "final solution" for me (since I like to put one of Tubb's bubbles on the end of the barrel [3/4" band an inch long] and a 5/8"x24 thread in front of that for my muzzle brake) is to recess the muzzle an inch or more. PT&G makes a reamer (is something like a floating pilot chamber reamer) for doing the last detail on the crown back in there. Might use a boring bar for most of the work and the reamer to finish it.

Another reason I'm inclined to the 30 degree, is that the reamer could be later used (with a simple tight slip-fit bushing to go over the 3/4" part of the barrel band with a hole in front of the muzzle this is an exact fit for the reamer (could be drilled through with the reamer when the chamfering is done). To use the very simple bushing, just take the bubble and the brake off, tap the bushing on and away you go to clean up the recessed muzzle a bit. Maybe could do the same thing with a 90-degree reamer. Humm . . .

With the 5/8"x24 thread, the back bore on the muzzle should be under 0.34" to give the brake plenty of metal underneath the threads. I don't know is that's tough to do with a boring bar.

Sending Dave Kiff a cad-drawing of my "wild idea" and see if he thinks it will work. Not knowing anything about rifle smithing, maybe Preacher could give a clue if he thinks this would be an easy fabrication for a smith.

On the cleaning controversy, saw John Krieger mention on Utube that its not "the brush", its "the debris" from the barrel on the brush. Tough particles like in a lapping compound. I'm too poor to be buying another barrel, so I'm figuring the angles to make this one last.

I really appreciate the great insight all you guys have. Always sets me thinkin'. Thanks!

 

[WayneShaw]

Why do you feel it necessary to recess the muzzle/crown? You have the end of the barrel already cut down twice, one for the 3/4" device and then 5/8"for a brake. And you want to put the crown back inside that? If you want to be able to touch up the crown, why not just use a center cutting tool that uses bore bushings?

It is amazing all the methods of cleaning a barrel. Bronze brush, no brush. Pull a brush, don't pull a brush. Nylon brush? JB compound? Never let JB be pushed out the end of a barrel? Solvent types? Copper solvent?

If you compete, a barrel is an expendable component. They don't last forever. They are a tool. They need to be kept in a consistent condition, whether clean, some copper, carbon buildup, it has to perform the same each time. Regardless of how you do it, if cleaning is done right, it will not wear a barrel out faster.

 

[JRS]

Why do you feel it necessary to recess the muzzle/crown? You have the end of the barrel already cut down twice, one for the 3/4" device and then 5/8"for a brake. And you want to put the crown back inside that? If you want to be able to touch up the crown, why not just use a center cutting tool that uses bore bushings?

It is amazing all the methods of cleaning a barrel. Bronze brush, no brush. Pull a brush, don't pull a brush. Nylon brush? JB compound? Never let JB be pushed out the end of a barrel? Solvent types? Copper solvent?

If you compete, a barrel is an expendable component. They don't last forever. They are a tool. They need to be kept in a consistent condition, whether clean, some copper, carbon buildup, it has to perform the same each time. Regardless of how you do it, if cleaning is done right, it will not wear a barrel out faster.

Sounds like a man who knows a little something about a rifle barrel Use your nylon brushes for scrubbing out the toilet ;D

 

[hogpatrol]

As an experiment, I had a bud push a bronze brush through my dirty barrel while I held an open palm under and just forward of the muzzle. As the brush exited the muzzle and the bristles sprung back, a load of cleaner & debris was deposited in my hand. I figured if I pulled the brush all the way back to the the chamber, some of that stuff would be deposited there, in bolt lug recess, magazine area and trigger. Since then I have removed my brushes. As far as wear is concerned, I've never seen a worn out butter knife.

 

[scpaul]

Excuse me, For my info. I don't know enough to take a side. Wouldn't the bbl. by benchrest ,etc. standards of accuracy be worn out before the bronze brush did any real damage ? Still tryin' to learn....Paul

 

[butchlambert]

As an experiment, I had a bud push a bronze brush through my dirty barrel while I held an open palm under and just forward of the muzzle. As the brush exited the muzzle and the bristles sprung back, a load of cleaner & debris was deposited in my hand. I figured if I pulled the brush all the way back to the the chamber, some of that stuff would be deposited there, in bolt lug recess, magazine area and trigger. Since then I have removed my brushes. As far as wear is concerned, I've never seen a worn out butter knife.

I guess my post disappeared. hogpatrol, if what you are saying is happening, you don't use a boreguide. That is what they are made for.