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Sidelock
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Found a couple more 10g in my files measured by a friend; both 3 frame pattern welded Parkers and both with bores .794"
#1 end of chamber .140"; 9" from breech .093" and 9" from muzzle .050"
#2 .114"; .059" and .040"

All the below had standard bores and chamber length and were felt to be unaltered

End-of-chamber:
3 No. 1 1/2 frame 12g fluid steel Parkers were .088", .092" and .105"

4 No. 1 frame 16g fluid steel Parkers were .084", .100", .105" and .111"

No. 0 frame 16g fluid steel Parker .104" L and .099" R

A No. 0 frame 20g fluid steel Parker was .091"


http://parkerguns.org/forums/showthread.php?t=31521
12 gauges
Baker Paragon L-.97, R-.103 2 5/8" chamber
Win 21 L-.115, R-.119 2 3/4" chamber
LC Smith Field L .102, R .105 2 3/4" chamber
Parker PH L .107 R .115 2 1/2" chamber, 1 frame
Parker VH L .90, R .90 2 5/8" chamber, 1 1/2 frame

More numbers
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=379803&page=3

http://parkerguns.org/forums/showthread.php?t=1565&page=4

English:
James Purdey (1898) 12b., 2.5" chambers: ≥ 0.100.
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.098
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.103
Boss (1897-8) 12b., 2.5" chambers: ≥ 0.090
Westley Richards 12b., 2.5" chambers: ≥ 0.090
James MacNaughton (1895) 12b., 2.5" chambers: ≥ 0.095
Wm. Pape (1898) 12b., 2.75" chambers: ≥ 0.100
EM Reilly (1887-1904) 12b., 2.5" chambers: ≥ 0.091
Henri Egg (1870) 12b., 2.5" chambers: ≥ 0.108
WH Monks (1875-87) 12b., 2.5" chambers: ≥ 0.116
WC Scott (1905-6) 16b., 2.75" chambers: ≥ 0.105
Francotte (1938) 12b., 2 5/8" chambers: ≥ 0.098
Westley Richards (1905) 20b., 2.5" chambers: ≥ 0.098
WW Greener (1922) 20b., 2.75" chambers: ≥ 0.098

Belgian:
Francotte (1894-5) 12b., 2.5" chambers: ≥ 0.085
Francotte (1896) 12b., 2.5" chambers: ≥ 0.085
Francotte (1930) 20b., 2.5" chambers: ≥ 0.095

French:
Verney Carron (1950s) 12b., 2 5/8" chambers: ≥ 0.100

German:
Wilhelm Brenneke (1902) 12b., 2.5" chambers: ≥ 0.110


Wall thickness recommendations are dependent on the tensile strength of the barrel steel and pressure of the load for which the gun was designed

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Sidelock
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Some time back, I posted a description of the horizontal method of measuring wall thickness with a Manson gauge. This is not a recommendation, only a different method. By the way, Mr. Hosford kindly demonstrated the horizontal method to me, yes, on a Manson gauge. Previously, I had been using the vertical method. The drawback of the vertical method is that it is impossible to use at a gun show table. With a helper to hold the barrels in place, the horizontal method can be used on a table.

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mc Offline
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Mr eightbore you can put the but of the gun on the ground have Mr seller or buyer hold the gun check from the muzzle .you can check from the breech by taking the barrels off but if you get acceptable results your happy with checking horizontal then that's what you should use

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Sidelock
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doc drew, thanks for sample measurements...they seem to validate my 90/30 standard, as passed on to me by old ed, the gunsmith...who has also passed on...i am sometimes lost without the confort of having access to his knowledge and wisdom...


keep it simple and keep it safe...
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mc Offline
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Edd don't be so hard on your self I'm sure your lost most days when you wake up

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Sidelock
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G.T. Garwood (Gough Thomas) Shooting Facts and Fancies, Chapter 34, 1978
Gives an average of .114” for end-of-chamber wall thickness for mid-20th century English 12g guns, but observes that higher tensile strength steel allows for lower wall thickness.

Jack Rowe demonstrates use of a vertical gauge starting at 2 minutes.
He states his lower limit is .020”, but clearly in reference to the distal 1/3 of barrel and he never addresses end-of-chamber wall thickness.


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Sidelock
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Larry Potterfield using a vertical gauge, but no mention of MWT

https://vimeo.com/352737273

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mc Offline
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That's Len bull walking on in the begining

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Boxlock
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Originally Posted by mc
Edd don't be so hard on your self I'm sure your lost most days when you wake up


Lol. Tough crowd.

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Sidelock
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Apparently, some Brit guns (i;e;: 2" 12b guns) were built with barrels as thin as .018, sometimes less. So they were proofed and left the factory with barrels less than 20 thousandths of an inch. It all depends on the intended use and, of course, on passing proof spec for the cartridge designated.

As Jack Rowe states in his video, the measurement 9" from the muzzle is usually the thinnest, where the pressure has diminished significantly with a nitro cartridge. So, a gun might have .015" thickness at that point, or perhaps less, and still pass proof, but it would dent very easily and would not be thick enough to safely repair the dent.

My main 'smith, Pete Mazur, uses an ultrasound thickness detector. Interesting to watch - a lot like a medical ultra sound procedure.


C Man
Life is short
Quit your job.
Turn off the TV.
Go outside and play.
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