polish the throat

No.

The only time I have heard of this was when Lothar-Walthar recommended polishing the throats on their L-50 barrels. This was in response to gunsmiths complaining about really rough finishes.........jackie
 
A barrel maker has told me if you WANT to you could short stroke a tight patch in the throat with Iosso, JB, or something of that nature, but I don't think he does for his own stuff, and that's what I do (or don't do).
 
I don't think centerfire gunsmiths polish the throat/lead..you might ask you question on the rimfire forums since it is a pretty common practice on rimfire competition barrels...



Eddie in Texas
 
Throat Polishing

eww1350 said:
I don't think centerfire gunsmiths polish the throat/lead..you might ask you question on the rimfire forums since it is a pretty common practice on rimfire competition barrels...



Eddie in Texas
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I know for a fact that a lot of guys in rfbr. use a nylon brush, patch wraped, with Ioso paste to polish that throat area. Some exsesilivy..? The main purpose is to elimanate a "carbon ring" that will devolop just after the chamber lead, and this is a bad thing.( the ring that is) Others will do same with a newly chambered bbl. Throat polishing is yet again a "matter of opinion" imo. My highly expieranced gunsmith, will tell you that too much of that is not good for your chamber. Makes sense to me. Ed.
 
PR2:

The barrel I'm working on now is a .267 6mm Dasher fire form barrel.
I would be interested in what you use.

Ed:

What I was wondering about polishing is the tooling marks, on the 1&1/2° slope on the rifling's, left by the reamer.
I just wanted to lightly polish the the sloping surfaces of the rifling's with out wallowing out the throat.

The chamber finish looks great. I'm not sure why the throat doesn't look as smooth. Maybe because this is a rechamber job on a used barrel.

Hal
 
Every reamer cuts differently but in a nut shell that angle is cut in a shearing motion. Never smooth but some reamers are better than others. There will also be a wire edge on the trailing side of the land and also there can be an edge pushed up at the end of the freebore section in the groove area. And I do polish throats. I have for about 9 years now on every barrel that comes through the shop.

Dave
 
Dave Tooley said:
. There will also be a wire edge on the trailing side of the land and also there can be an edge pushed up at the end of the freebore section in the groove area. And I do polish throats. I have for about 9 years now on every barrel that comes through the shop.

Dave
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After I bought my lathe I started out doing 22lr's because of $40 reamers and $75 Annie bbl blanks from Numrich. Didn't want to start out doing 50,000 psi stuff :).The guns would shoot ok but throw flyers pretty regularly. Got discouraged. Later got determined and bought a borescope. "A-HAHA !!!!!!!! Those burrs on the rifling can't be doing the bullet any good !!! " I then used a simple split arbor and worn 600 paper to eliminate the burrs. Stone axe but it worked. I also polish with FLITZ for a really smooth surface. The bolt was noticeably easier to close which made sense one I thought about it. This bbl probably had 500 to 600 rounds down it which tells me that a lead bullet bbl will never have the reaming burrs smoothed out by shooting standard target bullets.

Then I figured out about removing bullets for slugging bbls. "Hmmm, loose after the choke. Cut off about 1/2" and recrowned [ radius crown of my own concept ]. After some ammo testing and tuner twisting that little homebuilt 40X one day spit out a 5 shot, 50 yard .059" group [ measured by the scorer at the next CF BR match ] . The straight bore with choke 19" bbl won't really get it done for serious BR but it knocks over 200 yd rams with boring regularity at a local club match.

Then I got to thinking and the first cf bbl I did [ 6 Beggs ] I looked at the leade with the borescope. Yep same stuff as the RF's. Used the same concept and polished those out before shooting. Even did the Flitz. Ain't shot the gun enough to see how it shoots.

As I cogitated on the CF chamber burr situation I came to the conclusion that the jacketed bullets and the 50 to 60,000 PSI flame quickly do away with the burrs and surface roughness. The burrs get embedded in the bullet jacket of the first few bullets and are carried down the bore and away. Is this really how you want to treat a brand new high dollar bbl ??? I wonder how many hummers have been killed by the jagged burrs scratching the rifling down the whole length of the bbl ?

I have looked at probably 15 or more RF BR bbls done by some name 'smiths and the majority had the burrs. It actually surprises me when the leade doesn't still have the burrs "WOW somebody did it right ! "
 
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And not being able to look at the chamber and bore has soured me on messing with the 17 rimfires !!!
 
Dave Tooley said:
Every reamer cuts differently but in a nut shell that angle is cut in a shearing motion. Never smooth but some reamers are better than others. There will also be a wire edge on the trailing side of the land and also there can be an edge pushed up at the end of the freebore section in the groove area. And I do polish throats. I have for about 9 years now on every barrel that comes through the shop.

Dave
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I wonder if properly polishing the throat after chambering completely eliminates the whole "bbl break-in" concept ?

Any insights Dave ?

Thanks
 
Polishing Throats

I've been polishing all my throats after chambering for the last 5 years and have found it eliminates the need for a Barrel breakin routine!!
I use the VFG felt pellets and Brownells Abrasive Compound 400 Grit Silicon Carbide #083-045-400
The very first 15 rounds shot on my Krieger and Bartlein Benchrest Barrels produce no more coppering that the same barrels with 5-600 rounds shot. (which is almost none!)
 
Back when BC frequented the rimfire forum, he talked about using a hob (his term) to finish a chamber, but never gave any details. I suspect this discussion is getting close to what he wants to accomplish his procedure.

Also Gordy Gritters talked about lapping a bore with 150 to 220 grit aluminum oxide, in the following thread:

http://benchrest.com/showthread.php...-used-to-lap-barrels&highlight=barrel+lapping

I suspect polishing a throat would take a grit that's more coarse than you'd think. JB on a patch wouldn't do the job.

Regards, Ron
 
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My curiosity got the best of me. I chambered a barrel last weekend, looked at the throat and it looked like any fresh cut chamber/throat. So I took a short cleaning rod, bronze brush one size down, and wrapped a patch real tight around the brush. I took some Flitz and smeared it on the patch while rotating it in the direction a wrapped it, letting it soak into the patch. Put the barrel in a vise and short stroked the throat for maybe 20 cycles, didn't count them. Cleaned it out and looked again, a very noticeable difference in the way the throat finish looked. I can't imagine Flitz causing much harm or wear in such a short amount of use, but it sure did take the radial tooling marks off the throat.
 
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