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Joined: Oct 2005
Posts: 65
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OP
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Joined: Oct 2005
Posts: 65 |
I've got NID 425371 which I thought was unmodified. Barrel flats markings indicate its choked 2 and 4 for mod and full. I just measured the bore diameters (with an inexpensive digital caliper not a bore micrometer)at the muzzle and they measure .719 and .699. Assuming a .729 standard 12 gauge bore, thats only .010 and .031 choke constriction which is more like IC and IM. Have my chokes been opened or did NID bores run larger than the nominal .729? I don't have a bore mic so I can't measure it. The barrels are 26 inches which I know was the factory length so it wasn't shortened. Any insight would be appreciated, thanks. John
Last edited by John C; 11/10/06 11:43 PM.
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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 |
Thy the ultimate choke gauge! Shoot it on paper.
bill
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Joined: Jan 2002
Posts: 5,946 Likes: 144
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,946 Likes: 144 |
I owned a Grade 1E NID 12-gauge in the 441,xxx range with 28-inch barrels marked 2 and 4. It was way over-bore -- .749" left and .744 right. Chokes were .009" right and .033" left. My 12-gauge 4E Skeet with all the bells & whistles marked S and S has bores .730" left and .729" right with chokes .016" left and .009" right. Going through my notes on the various NIDs I've owned in all gauges, I find the guns made 1935 and earlier are all over-bore while those made 1936 and later within a thou or two of true.
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Joined: Dec 2002
Posts: 597 Likes: 15
Sidelock
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Sidelock
Joined: Dec 2002
Posts: 597 Likes: 15 |
I have a copy of an "Ithaca Gun Co., Inc. Ithaca, N. Y." drawing number "T-113" which is titled " Standard Bore, Chamber & Choke For Shotguns". It was drawn by "NFS" on 3-10-39. With one minor revision on 11-6-45.
For both 12 and 12 Mag. the:
Bore diameter is listed as 0.729;
Full choke is 0.693 dia and 2 1/2" long;
Imp Mod is 0.702 dia and 1 7/8 " long;
Mod is 0.711 and 1 1/4" long;
IC and Skeet is 0.720 dia 5/8" long and
Cyl is 0.729 and 0" long.
The length of the choke is where the choke begins at bore diameter to the muzzle end. For example, full choke starts back 2 1/2" from the muzzle at 0.729 bore diameter and ends at 0.693 at the muzzle. No clue about taper or rate of change.
As pointed out, this is a 1939 dated drawing so anything prior to this could be different.
Don't know if this helps but there it is.
Bill Jolliff
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Joined: Oct 2005
Posts: 65
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Guys thanks. Researcher since mine is a 1926 gun I'm assuming its overbored .740 or so which would then make my constrictions at the muzzle .020 and .040, more typical mod and full choke constictions.
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