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Forums10
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Mar 27th, 2026
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Joined: May 2010
Posts: 1,548 Likes: 112
Sidelock
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Sidelock
Joined: May 2010
Posts: 1,548 Likes: 112 |
410 or if memory severves 36 bore is a nominal size as is 12 bore. It may well be that two shotguns of the same caliber from the same manufactuer have differing bore sizes. In old English proof size there was only .005 between the sizes of a "410" and many were actualy proofed at anything btween .400" & .415".Makers try to standardise there prduction but if a barrel becomes "over size" ,why throw it away when it can easily be bored up to the next size?
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
The .410 has been at various times marketed as both a 36 gauge as well as a 12mm. Both designations are of course incorrect. 36 gauge = .506" diameter. 12mm = .472" diameter, or about the size of the head of the shell, no other sizes of shotguns are so specified, always the bore diameter.
.410 is actual decimal size, not a gauge as such & it measures "Guess What" .410". This is the nominally correct size for a .410. Manufactures could of course apply their own thoughts to the actual size used as well as they had manufacturing tolerences. A bore of .400' = 72.68 gauge & one of .420" = 62.78 gauge. ±.010" should cover most variations of a .410 "Caliber" shotgun.
The "Gauge" of a barrel having a bore diameter of .410" = 67.49
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Joined: Feb 2002
Posts: 2,859
Sidelock
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Sidelock
Joined: Feb 2002
Posts: 2,859 |
I used to have an actual 36 guage ML and posted a picture of the end of the barrel adjacent to a .410. Here is the link for anyone who wants to see the picture http://www.fourten.org.uk/36g410.htmlSteve
Approach life like you do a yellow light - RUN IT! (Gail T.)
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Joined: Dec 2001
Posts: 12,743
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 12,743 |
Interesting pic Rockdoc. This very graphically shows the difference between a .410 & a true 36 Gauge. I quickly measured a fired RP .410 hull & got .480" for the head just in front of the rim & a rim diameter of .533". Thus if dropped into the bore of that 36 open end first it would be stopped at the rim but the entire hull would simply rattle around in the bore.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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Joined: Dec 2001
Posts: 2,961 Likes: 9
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 2,961 Likes: 9 |
I have a friend who had real trouble with his 4 bbl K-80'a 410's, the forceing cones were ROUGH and patterns poor. He spent hours polishing them and it all bore fruit when he broke the intersecting bore/forceing cone junction makeing sure there was no sharp joint. The same guy polished my Briley forceing cones and it was a major improvement on 28, and 20 (I now use .002 choke in both for skeet) The 410 was so much better that it hard to believe, 23 more bb's in my pattern, something like 13% better. I strongly recomend the polish job for 410 tubes and a close check of that area on barrels.
bill
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