Barrel Wall Thickness

[TARNATION !!!]

Bruce: On that 20 ga, based on the .008 loss per honing, those barrels would have been honed at least 3 times to get down to .006 if starting at .030 if I got the math right. This leads to my continuing education questions.

Does honing serve a practical purpose verses a cosmetic purpose?
Does light pitting cause problems for continued shooting?
Hypothetically, does a single deep pit [let's say it leaves .020 at that spot] have the same potential for barrel destruction as the honing to remove it or would honing the entire barrel be far more problematic?
Finally, is there a means to fill a pit and leave the bwt alone, as opposed to remove steel to the depth of the pit thereby reducing bwt over the entire barrel length?

Drew: The barrel schematic shows no forcing cone. I'm wondering about bwt around the cone. Thoughts?

Thanks,
Jack

[Bruce Day]

Jack, here's my take on it. I know others have studied the issue also, and I am a big fan of the Bill Murphy philosophy of "don't mess with them".

1. No, except that unpitted bores are easier to clean. So just scrub more.

2. No

3. Don't think so. Would you rather have a small single isolated potentially weak spot or would you rather have the entire barrel length potentially weak?

4. Don't know, other than a full length liner, which is a drastic and expensive remedy.

[Drew Hause]

"Is there a means to fill a pit?"

I've discussed with a few TIG specialists, and no.

[TARNATION !!!]

Drew: So we can rule out TIG welding. I have often wondered if some of the advanced epoxy resin systems might fill a pit without resorting to welding. Is there something inherently wrong with epoxy/steel combo that is made flush to the inside of the barrel?? Don't know, just asking.
Cheers,
Jack

[Bindlestiff]

Originally Posted by Drew Hause

The Field March 7, 1891 Vol 77:325
http://books.google.com/books?id=inQ...=0#PPA9-IA6,M1



UK Working Standards recomended minimum wall thickness measured 18" from the barrel breech from Double Gun Classics p. 56, Vol. 1, No. 4 Jan-Feb, 2006:
2 1/2" 12g- .028
2 3/4" 12g- .032
Re-proof recomended minimum- .024

The Hunter's Encyclopedia from the German proof house: minimal wall thickness at end of chamber, regardless of length, for 12, 16 & 20 gauge guns should be 2.3mm (.0906") for 'ordinary good steel' or 2.1mm (.0827") if a 'Special Steel' was used. For the 24 & 28 gauges, due to their higher pressures, 2.4mm (.0945") was recommended.
Minimal wall of .6mm (.0236") was recomended in the "forward third" of the barrel.

Thanks Drew, I incorporated this information and some of the other comments to improve this FAQ.

Thank all for your input, it helped too.

[Twice Shooter]

Dr. Drew,

Please check your PM. Tom

[Jim Kucaba]

Originally Posted by Robin Lewis

Thanks Drew, I incorporated this information and some of the other comments to improve this FAQ.

Thank all for your input, it helped too.

Robin ... What a great illustration ! ... I hope everyone prints several copies for future reference ... THANKS !

Jim Kucaba ... AriZOOna Cactus Patch ... Email: JimKucaba@aol.com

[VH20]

Bruce,

Your example of taking .008 from the BWT for a first "honing" seems extreme. To remove this much metal, usually they would be reamed instead of honed, but that's just academic to this discussion. The point I want to make is that using your example of taking .008 from the BWT would mean adding .016 to the bore dia. So, a typical .730 bore would now be .746 after one reaming, and a second would make the bore a whopping .762.

I have found that reaming in steps of .005 over bore dia. often cleans up most pitting, and if not, another .005-over usually will. In the first case, you only take .0025 (two-and-a-half thousandths) off the BWT, and in the second, still only .005. If necessary, we could go up another .005 and now be .015 over original bore dia. (.745), yet after three reamings still not have taken off quite as much as your example of one reaming (.0075 vs. your .008). There is a reason bore reamers are typically sold in .005 increments. But you have to remember that reaming x-thousandths from the bore only removes 1/2x-thousandths from the BWT.

All that said, I agree with you and Bill. Really not much reason to fool with it in the first place, and I usually don't.

Jim

[Bill Murphy]

I have a Parker that was pitted when I got it and it doesn't seem to be pitted now and I never did anything to it except scrub and shoot it for many years. I also bought a "ruined" A Grade Fox 16 gauge several years ago. After a very agressive scrubbing session, the barrels were as new. I think some "minor pitting" is really surface rust. It isn't rocket science to mic the inside of the bores and compare the measurement to the known standard. Some exceptions to the Parker standards were on the big side, but I think we know what is unreasonable and indicates a hone job.

[VH20]

Bill,
Are you using your discarded sheets of old sandpaper to make shot-column wraps for your reloads? ;-)