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Measuring shotgun choke diameter

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Measuring shotgun choke diameter

Unread postby CFII » Wed Jan 21, 2015 12:06 am

Is there a quick way, like with a coin or something, to tell the choke of an unmarked 12 gauge barrel?
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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Wed Jan 21, 2015 12:51 am

If I remember right, a dime won't go in a "full" but will in a " modified "

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Re: Measuring shotgun choke diameter

Unread postby Tim McCormack » Wed Jan 21, 2015 10:01 am

Glenn is right, as usual, to a point. The old dime trick does identify a full choke in "normal" guns but won't tell you what it is if the dime does go through. Also if the barrel has been modified by "backboring" ( which is sometimes done to increase the amount of choke ) it won't really be accurate either.

The amount of "choke" in a shotgun barrel is actually the difference between the bore diameter just before the constriction and the diameter of the constriction. In a 12 guage barrel a full choke will have about .035" difference, whereas a modified choke will have about .019" difference, and an improved cylinder will have only about .009".

The nominal bore diameter of a 12 guage barrel is .729" If you have a set of machinists expanding calipers you can get an idea of the choke by measuring the diameter of the choke constriction and then compare it to .729".
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Wed Jan 21, 2015 10:40 am

Today many new guns are Over Bored as well as back bored. Any gun shop with a gunsmith on site, should be able to measure it as there is a standard Choke Gauge, again as Tim pointed out, which might not be exactly that accurate regarding what performance you might get. If it is an old gun the dime trick should be (use a new shinny dime! :D ).

What kind is it? Most fixed choke shotgun have a choke designation at the beginning of the barrel somewhere. "$" for skeet etc.

Performance wise, things are getting technical on the new shotguns. Back Bore, Over Bore, Lengthened Forcing Cones. If the shotgun is not a classic and has enough metal in the barrel, you can get it threaded for screw in chokes pretty reasonably. Then you not only will know what you have, but can change the constriction to what ever you want.

If you go to any of the new screw in choke suppliers , (Briley, Muller, Carlson, Trulock etc.) they will list what the various restrictions are. Today there are a lot more chokes available then in the past. Spreadeer, Cylinder, Light Skeet, Skeet, out to Full and Extra Full. I have screw in chokes now in all my shotguns except my early Browning Citori 4 Barrel Skeet set, which all 4 barrels are SK/SK.

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Re: Measuring shotgun choke diameter

Unread postby CFII » Wed Jan 21, 2015 9:16 pm

Cool, thanks, the dime indicates full choke, not even close to going in, although both the 12 gauge and the 30:30 barrels have M stamped on them. It's an heirloom that came back into my control after over 50 years, a single shot break open Savage with switchable barrels.

The gunsmith says it's fine just because of his firing pin tape test but, 50 years ago the 30:30 barrel wouldn't fire. Hopefully it was too humid ammo although all other ammo stored in same closet was good.... Will test in woods soon.
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Re: Measuring shotgun choke diameter

Unread postby Tim McCormack » Thu Jan 22, 2015 8:40 am

I'm not familiar with the "firng pin tape test" but presume he was trying to measure the amount of firing pin protrusion when the hammer is dropped. If I remember correctly, that gun has a retractable, spring loaded, firing pin that retracts after firing. The forward momentum of the pin after being struck by the hammer is what actually makes it hit the primer in the shell/ cartridge. It returns to rest with the tip behind the breech face so that the barrel can be opened and closed.If it stuck out the barrel wouldn't open past it. I've seen that happen when the spring breaks and allows the pin to stay forward. It's also a safety measure. It keeps the firing pin from laying against the primer.

If the shotgun barrel fires and the rifle one doesn't, the head-space in the rifle barrel may be too deep allowing the cartridge to set too far forward for the firing pin to strike it hard enough to fire it. Compare the firing pin indent on the shot-shell with the one on a 30/30 cartridge after you (try to) fire one. If the cartridge won't go off you'll most likely see a light blow on the primer.

The 30/30 is a rimmed cartridge so the head-space is determined by the depth of the counter-bore in the barrel where the rim sits. If it's too deep there isn't much you can do to fix it on that style gun.

There is also a slight possibility that the rims on the cartridges are undersized allowing the primer to be too far forward when in the barrel, but it's only a slight chance.
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Re: Measuring shotgun choke diameter

Unread postby CFII » Fri Jan 23, 2015 12:16 am

It's a Savage Arms Model 219 with no visible hammer. The gunsmith's "firing pin tape test" doesn't inspire too much confidence in me for actual firing pin power, since he just taped over the pin hole, closed the empty action and dry fired, getting a hole through the tape. I'll test fire it soon for real.

I had an adjustable choke installed on an old ventilated rib Winchester 1200, since I used it for everything including 12 gauge rifled slugs and it was curious to see gun users sometimes think that it was to be adjusted as a bird flushed, then shoot!
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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Fri Jan 23, 2015 1:13 am

I had a Sears & Robucks 12ga auto back in the late 60s with a poly choke. I would crank that thing down as hard as I could, way past the full mark till it stopped turning. I kicked ass on the long shots, even with OO buck.

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Re: Measuring shotgun choke diameter

Unread postby RKittine » Fri Jan 23, 2015 7:14 am

My first shotgun was a Mossberg 12 gauge pump with a Vent Rib and Poly (Adjustable) Choke. Pretty ugly, but it worked. Now on most of my shotguns I have screw in chokes.

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Re: Measuring shotgun choke diameter

Unread postby CFII » Sat Jan 24, 2015 5:56 am

The poly chokes "look" great, like a secrete weapon, which they kind of are....
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Sat Jan 24, 2015 4:25 pm

Only thing uglier than a Poly Choke (on a shotgun) is a Cutts Compensator!

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Re: Measuring shotgun choke diameter

Unread postby CFII » Sat Jan 24, 2015 5:24 pm

Yeah "looks" is a weird thing. A sleek barrel looks restricted in its capabilities compared to a Poly Choke....
What's that compensator compensating for ?
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Sun Jan 25, 2015 8:03 am

The Cutts Compensator helped control Mussel Jump prior to the current technology of angles barrel porting. On the Skeet, Trap, Bunker, Sporting Clays or 5 Stand Range, most shooters do not want to have anything at the end of the barrel that hinders their view. For this reason, most American Trap (one target one shot) shooters have switched to full size Over / Under Frames, with a single barrel on the bottom and a very high narrow rib going from the bottom barrel all the way up to where a High Rib would end on a two barrel O/U. See Browning Cynergy Unsingle or equivalent.

Many clay shooters remove both the end sight or bead on their shot guns and the middle beat if there is one, so that there is no sight distraction. A really good clay shooter (or for that matter bird hunter) will shoot a shotgun with both eyes open and look at the target only, to the extent that is possible, hence nothing on the barrel to distract them, for with a correctly fitted shotgun and a proper mount, the shotgun barrel should be come an extension of your sight path without looking at it.

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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Sun Jan 25, 2015 10:32 am

Bob, imo they all should shoot stock single barrel H&R 12ga and find out who can really shoot

Glenn
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Sun Jan 25, 2015 11:04 am

Why 12 gauge Glenn. .410 is a better indicator of who can shoot, unless we are talking about a single shot 12 gauge for Doubles! :o A bolt action .410 for doubles would be a hoot. Maybe even out of a TC Contender with the .410 barrel. I still have a box of No. 9 .44 Mags that would work in my .44 mag Contender Barrel - 10". Too long for my Model 29 - 8 3/8". Now .22 LR Birdshot would be a real challenge.

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Re: Measuring shotgun choke diameter

Unread postby CFII » Tue Jan 27, 2015 5:05 pm

My younger brother claims, witnessed by our cousin as teenagers, to have used the single shot break open 12 guage I mentioned above to first bag a flushed Ruffed Grouse from a pair and then quickly reloading, bag the other one! He knew where they were hanging out and walked in fully alert for his plan.
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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Tue Jan 27, 2015 5:37 pm

Bob, money helps beat the guys with talent. CFII, some guys are quick enough to make it work.


This man takes archery from historic times, adopts it, and takes hand/eye/body coordination to an art form. You will be hearing more from this fella.



His skills are truly beautiful to watch!! Bill G.


https://www.youtube.com/watch?v=BEG-ly9tQGk

Glenn
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Tue Jan 27, 2015 6:19 pm

Interesting. Lots of talent there, but I will stick with my shotguns. I am just starting to shoot registered Skeet again. I owned a couple of bows over the years, but gave up archery a long time ago.

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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Tue Jan 27, 2015 6:27 pm

The point I was trying to make was if skeet is shooter against shooter then take the gun out of it and let them shoot the same one

Glenn
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Tue Jan 27, 2015 8:15 pm

I think you may be downplaying the effect that fit has on shotgun shooting. Not like lining up iron sights on a rifle or pistol. For most shooters if the gun fits and mounts well, it will become an extension of your arm and where you are looking.

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Re: Measuring shotgun choke diameter

Unread postby CFII » Tue Jan 27, 2015 9:12 pm

Great archery film! I've always done contra lateral, empty bow draws when practicing for more balanced muscle development but the last few years started shooting from the other side (suited draw arm is slightly awkward on modern compound bows) with about equal accuracy.
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Re: Measuring shotgun choke diameter

Unread postby cubdriver2 » Tue Jan 27, 2015 10:08 pm

RKittine wrote:I think you may be downplaying the effect that fit has on shotgun shooting. Not like lining up iron sights on a rifle or pistol. For most shooters if the gun fits and mounts well, it will become an extension of your arm and where you are looking.

Bob


Ok, you can shorten the stock if you want. Those that are truly good adapt to what ever needs doing. Anything else an excuse.

Glenn
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Wed Jan 28, 2015 9:11 am

After "Fit" the biggest difference between the lower priced shot guns and the higher ones (If you forget about grade of wood, engravings etc. which I agree does nothing but support your ego) is in strength of the gun. For a hunting shotgun that maybe gets a few hundred rounds through it a year no big deal. For a registered shooter that may shoot 12,000 practice shots a year and another 5,000 or so registered targets, it makes a big difference.

My Caesar Guerini Game guns are warranted for life, get a free tune up every year and have been know to go well over 1,000,000 rounds without fault.

Pattern a group of shotguns and you would be surprised at the variations of rib verses where the shot is really going etc.

There is no argument that a more expensive gun will not make up for a poor shooter. Since I only shoot clays, depending on the game, a single shot only works or American Trap.

Next time you come down to Warwick, we can run over to Thunder Mountain and shoot a couple of rounds of skeet or trap. You can pick the shotgun.

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Re: Measuring shotgun choke diameter

Unread postby Tim McCormack » Wed Jan 28, 2015 9:28 am

And don't overlook the positive effect a "better" grade gun for people had on my employment for the last 20 years of my 40 year career with Remington. :beer:
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Re: Measuring shotgun choke diameter

Unread postby RKittine » Wed Jan 28, 2015 10:07 am

Exactly (Check your E-mail Tim, I just blind copied you on an E-mail to Shane at the Custom Shop)

And, there is the whole Pride Of Ownership thing too.

I guess a "Blue Printed" and Trued 40XB Action with a squared bolt face, a polished and adjusted 40X Trigger, hand lapped barrel with a trued mussel crown, Pillar Bedded with a free floated barrel and a custom LOP, will not provide a more accurate rifle then a Mossberg 850. Right Tim?

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