March
S M T W T F S
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
Who's Online Now
6 members (susjwp, SKB, Hammergun, canvasback, Stanton Hillis, 1 invisible), 307 guests, and 3 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums10
Topics38,373
Posts543,979
Members14,389
Most Online1,131
Jan 21st, 2024
Previous Thread
Next Thread
Print Thread
Page 2 of 21 1 2 3 4 20 21
Joined: Nov 2018
Posts: 97
Likes: 8
Sidelock
Offline
Sidelock

Joined: Nov 2018
Posts: 97
Likes: 8
I make my own wall thickness gage similar to the one Drew has in his post. I have verified its reading via other methods such as cross sectioning
ultra sonic and eddy current. They all give the same reading within .0006" which wouldn't make the slightest difference.

1 member likes this: Drew Hause
Joined: Mar 2002
Posts: 7,693
Likes: 450
Sidelock
**
Offline
Sidelock
**

Joined: Mar 2002
Posts: 7,693
Likes: 450
What is really important? Accuracy and repeatability. If you get the "right" number, then it does not matter. Being able to check and verify that number over and over again gives you a bit of confidence. I have been using my setup for 20 plus years and checked it against known samples hundreds of times. When ever I find a thin area, I get real careful, but when going over a set of barrels, as long as the thickness is measuring above .025- .030 and is the same as areas nearby, I do not worry too much. If I find a area which is thinner than areas nearby, then I start looking for dent repairs and think about file work to blend the repair. If my setup is off .001-.005 I do not care as long as the walls are .025-.030+. I shoot several guns with barrels .020 as longs as the thin area is well towards the muzzle. But is is location and repeatability which my setup gives me consistently which is what I need. I know it is accurate because I have used it for decades and verified it with multiple other systems. We can not all be off the exact same way and same amount. Potential minor variations are not critical when you are talking about barrels not near a critical thinness. Mine are not. If I got to the point that .0006 was important then I would find a new gun.

Joined: Jan 2002
Posts: 506
Likes: 57
Sidelock
Offline
Sidelock

Joined: Jan 2002
Posts: 506
Likes: 57
The question about wall thickness just in front of the chamber was important to me, as I have a couple great old guns that have been lengthened from 2 1/2" to 2 3/4" chamber without reproofing. One was done by a very reputable gunsmith operation and they assured me it was safe to use. Both are over .100 right in front of chamber. I was doing research and found in one of Gough Thomas's books where he measured pre war English doubles and post war Italian, Spanish and Japanese guns. The English were from .106 to .122 with several in the .113 range. The post war doubles were .076 to .086. He also discusses elastic limits and a safety factor of 2, states a gun with working pressure of 3 tons should be .084.


This ain't a dress rehearsal , Don't Let the Old Man IN
Joined: Oct 2006
Posts: 2,260
Likes: 510
Sidelock
**
Offline
Sidelock
**

Joined: Oct 2006
Posts: 2,260
Likes: 510
I always use my gauges vertically. I have both the Manson style mounted to a wall and also have the British style wall thickness gauge, the type you’d find in most British & continental gunmakers shops. I much prefer the latter. My mitutoyo dial indicator is as good as it gets, and the readings when using that very rigid British style gauge are dead accurate and repeatable. If the gauge your using works correctly and you’re getting accurate readings, it doesn’t matter what type it is. I much prefer the British style gauge over the Manson though, but that’s just me.

Joined: Jan 2006
Posts: 9,398
Likes: 307
Sidelock
***
OP Offline
Sidelock
***

Joined: Jan 2006
Posts: 9,398
Likes: 307
Thanks for that data Nitrah.
The difference in Thomas' MWT recommendation is very likely related to barrel composition, and possibly service load pressure standards at the time of proof.
Turn-of-the-century pattern welded vs. decarbonized vs. pre-WWI Siemens-Martin 1030 vs. 1940s 4140 matters.

In 1925, the British 2 1/2” & 2 5/8” 12g maximum service load was reduced from 1 1/4 oz. 3 1/4 Dr.Eq. to 3 Dr. Eq. with 1 1/8 oz. shot with a mean pressure of 3 1/4 tons by LUP =
9,800 psi by Burrard’s conversion.
The 2 3/4” 12g max. service load was then 3 3/8 Dr. Eq. with 1 1/4 oz. shot with a mean pressure of 3 1/2 tons = 10,640 psi by Burrard’s conversion.
(Primarily for heavier “Waterfowl” guns)

And that is why it is difficult to provide generalized wall thickness recommendations.

Joined: Jan 2002
Posts: 9,718
Likes: 94
Sidelock
*
Offline
Sidelock
*

Joined: Jan 2002
Posts: 9,718
Likes: 94
blah, blah blah....

it is all meaningless, unless you establish some minimum standards for operator safety...

my standard is .090 in front of the chambers and .030, 7" down from the muzzles...


what are your standards?

sorry, for loosing patience, but you guys dance around this like a bunch of fairies...


keep it simple and keep it safe...
1 member likes this: keith
Joined: May 2022
Posts: 24
Likes: 10
Boxlock
Offline
Boxlock

Joined: May 2022
Posts: 24
Likes: 10
Slightly OT, but not worth a stand alone thread....

What are the nominal wall thicknesses for a 10ga? I see lots of info for 12ga, but not much for 10. I’d imagine the pressures (all things equal and applying common sense to loads) would be slightly less.

Joined: Jan 2006
Posts: 9,398
Likes: 307
Sidelock
***
OP Offline
Sidelock
***

Joined: Jan 2006
Posts: 9,398
Likes: 307
I've only seen one period 10g pressure report; from DuPont Brandywine Experimental Station data cited by Charles Askins in 1933
DuPont Bulk Smokeless Powder (not Oval used for the Super-X loads).
10g 4 1/4 Dr. Eq. 1 3/8 oz. shot = 10,662 psi + 10-14% for modern piezo transducer numbers

And have a single 10g measurement; a Smith hammer gun with Twist barrels
Bore .798"
End of chamber L .174" and R .167"
9" from breech L .095" and R .092"
9" from muzzle L .052" and R .050"

Joined: May 2022
Posts: 24
Likes: 10
Boxlock
Offline
Boxlock

Joined: May 2022
Posts: 24
Likes: 10
Thanks much. I appreciate the response and info.

Joined: Mar 2002
Posts: 2,857
Likes: 384
mc Offline
Sidelock
**
Offline
Sidelock
**

Joined: Mar 2002
Posts: 2,857
Likes: 384
Mr eightbore,,,i think it's a Manson I always check vertically , the mwt could depend on the steel I have some krupp barrels that are .80 in front of the chamber and 30 9 inches from the muzzle I have some old heavy barrels that are much thicker

Page 2 of 21 1 2 3 4 20 21

Link Copied to Clipboard

doublegunshop.com home | Welcome | Sponsors & Advertisers | DoubleGun Rack | Doublegun Book Rack

Order or request info | Other Useful Information

Updated every minute of everyday!


Copyright (c) 1993 - 2024 doublegunshop.com. All rights reserved. doublegunshop.com - Bloomfield, NY 14469. USA These materials are provided by doublegunshop.com as a service to its customers and may be used for informational purposes only. doublegunshop.com assumes no responsibility for errors or omissions in these materials. THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANT-ABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. doublegunshop.com further does not warrant the accuracy or completeness of the information, text, graphics, links or other items contained within these materials. doublegunshop.com shall not be liable for any special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of these materials. doublegunshop.com may make changes to these materials, or to the products described therein, at any time without notice. doublegunshop.com makes no commitment to update the information contained herein. This is a public un-moderated forum participate at your own risk.

Note: The posting of Copyrighted material on this forum is prohibited without prior written consent of the Copyright holder. For specifics on Copyright Law and restrictions refer to: http://www.copyright.gov/laws/ - doublegunshop.com will not monitor nor will they be held liable for copyright violations presented on the BBS which is an open and un-moderated public forum.

Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.0.33-0+deb9u11+hw1 Page Time: 0.073s Queries: 36 (0.051s) Memory: 0.8584 MB (Peak: 1.8988 MB) Data Comp: Off Server Time: 2024-03-28 11:43:38 UTC
Valid HTML 5 and Valid CSS