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Forums10
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Jul 28th, 2025
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Joined: Mar 2005
Posts: 709
Sidelock
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OP
Sidelock
Joined: Mar 2005
Posts: 709 |
Not a fine gun question, but you guys seem to know everything.
This is what I think I know:
Benelli is still .726 even with the new Ciro
Browning invector plus .733?
Beretta ciro plus .726???
Mossberg 835 & 935 .750
Perazzi .736
Please add or correct thanks.
With all these variations in bore diameter of the 12ga I am forced to admit that perhaps it would better be called a 12 bore then a 12gauge as it seems a standardization of bore diameter no longer exists.
What a revolting development!
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Joined: Feb 2002
Posts: 2,859
Sidelock
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Sidelock
Joined: Feb 2002
Posts: 2,859 |
I had a 12 gauge Crescent hammer gun that was "choke bored" and was bored .701 from the end of chamber to the muzzle in both barrels. Actually, what I think happened was they forgot to finish boring the barrels after they did the choke pass. Probably, a lunch break or end of day mistake. My first and last Crescent.
Approach life like you do a yellow light - RUN IT! (Gail T.)
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Joined: Jan 2002
Posts: 11,571 Likes: 165
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 11,571 Likes: 165 |
Pooch, I'm thinking more overbored than underbored. I measured the new Ruger Red Label at .739. Discovered that a new Guerini Tempio (20ga) was .625, so also overbored by .010.
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Joined: May 2010
Posts: 1,543 Likes: 102
Sidelock
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Sidelock
Joined: May 2010
Posts: 1,543 Likes: 102 |
As all European guns are now proofed in metric sizes they will be-
18,3 , 18.4 . 18.5 etc. for 12 bores that is equivalent to-
.720" , .724" ..728" etc. There may be a slight discrepancy in these equivalents but close enough. With .2mm or.008" between proof sizes .
Many makers now sell " back bored guns " which basically means over bored and these come in at any thing from 18.7mm /.732" to 18.9mm/.740" [average 18,8mm/.736"]
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Joined: Mar 2002
Posts: 7,893 Likes: 651
Sidelock
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Sidelock
Joined: Mar 2002
Posts: 7,893 Likes: 651 |
Over boring is nothing new. I have Bakers and LeFevers which are bored in the .745-.755 range. Newest on them is about 90 plus years old. Often a over bored gun throw very uniform patterns with modern loads. These days they over bore, elongate forcing cones, port the barrels and cryogenic treat the barrels. A lot of technology and hocus pocous go into each gun. Problem is figuring out what is real and what is hype.
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Joined: May 2010
Posts: 1,543 Likes: 102
Sidelock
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Sidelock
Joined: May 2010
Posts: 1,543 Likes: 102 |
[quote=L. Brown]Pooch, I'm thinking more overbored than underbored. I measured the new Ruger Red Label at .739. Discovered that a new Guerini Tempio (20ga) was .625, so also overbored by .010. [/quote
Most continental 20 bores are bored to 15.9mm or.626"as standard not the ,615" that the was used in the UK so it is not "over bored" as a feature just normal size for modern Italian guns.
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
0.729" is the "Mathematical" Standard derived from the weight of the round lead ball which would fit the bore. I do not believe there has ever been a time in the history of gunmaking that the makers have exactly followed that standard. There has always been variations due both to manufacturing tolerances as well as the makers idiosyncrasies. Many of the older guns such as the above mentioned Bakers & Lefevers were I believe intentionally over-bored with the idea they would most likely be used with thin wall brass shells using over sized wadding.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Joined: Jan 2002
Posts: 11,571 Likes: 165
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 11,571 Likes: 165 |
Nothing particularly new about a 20 that's .626 either. I had a Sauer from the mid-30's with that measurement . . . but, as was the practice back then, it was proofed as a 19 and so marked on the barrel flats. Not nearly as many numbers to keep in your head under that old system, when you knew--for example--that a 12/1 was overbore from the standard and a 13/1 underbore. But the fact that my 20 was marked 19 let me know immediately that if I measured, I should expect to find an overbore from what was then the 20ga standard.
Last edited by L. Brown; 06/25/14 05:37 PM.
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Joined: Jan 2002
Posts: 14,007 Likes: 1817
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 14,007 Likes: 1817 |
Perazzis can be anything from 18.4mm (.724") to 18.8mm (.740"). There is no "standard" bore dimension. Different dims for different guns and configurations, whether or not it has screw-ins or fixed chokes, etc..
My old Winchester imported MX-8, with 31 1/2" barrels and fixed chokes, measures .727" bottom and .725" top. Most that are imported into America have bores from .736" to .740", and the European models are tighter, as I understand it.
SRH
May God bless America and those who defend her.
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Joined: Jan 2002
Posts: 5,954 Likes: 12
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,954 Likes: 12 |
Over boring is nothing new. I have Bakers and LeFevers which are bored in the .745-.755 range. Newest on them is about 90 plus years old. Often a over bored gun throw very uniform patterns with modern loads. These days they over bore, elongate forcing cones, port the barrels and cryogenic treat the barrels. A lot of technology and hocus pocous go into each gun. Problem is figuring out what is real and what is hype. There is a very good modern method that will really sort. If you haven't done so, read "Performance of Sporting Shotguns" by Dr. A. C. Jones. He gives a method to shoot and analyze (the real statistical deal) patterns via digital photos and computers. Try it and you will find a lot of hype!! DDA
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