Choke constriction info.
 

I am checking out the bore diameter on a 12ga 30" GH damascus barreled gun using a Skeets Gun Shop dial indicator bore gauge.
Here are the following measurements. Both barrels seem identical within about .0015 at all of the increments.
Increments are inches from the end of the muzzle.

4"- .051
3"- .049
2"- .048
1"- .039
0"- .022
Leaving me with a choke of .029
Is there a constriction chart that will give me the ballpark equations for various constriction ranges? IE, .029= Mod, Full etc.?
Do the above constrictions and intervals sound realistic for an untouched bore as far as the bores not being honed etc.?
Checking wall thickness is next on the agenda.

29 thousands is a full choke

four inches of taper in a choke is not unheard of

as for charts - pick one

https://www.bing.com/images/search?q...tion&FORM=IGRE

but I am confused - a modern nominal 12 gauge is .729 - older Parkers were often a little over bored

are you saying that 4 inches from the muzzle - the bore diameter is .051?

12 gauge chokes....skeet is .004, IC is .009, mod is .018, imp-mod is .027, full is .036, x-full .045 Everyone has opinions, this is what I use for a guide. SXS oho

I came up with improved modified on the sight I saw on the internets.

Does the .017 constriction in the last inch sound normal?

This box contains many of James P. Hayes personal choke reamers. Most all are stamped with either his name, or his initials, along with the bore (12, 16, 20, etc) and are also stamped with dates between 1895 and 1903.
Without having a set of centers, some are difficult to measure as they are five fluted. This collection was given to a friend by Charley Parker, in addition to many other tools. They have since been passed to me. I also have James Hayes chamber rim cutters (all the way to 8 ga.) and a few chamber reamers.

Looking at the choke reamers, what is evident is that the cutting portion of the flights varies somewhat between 3 3/16" and slightly over 4" (20ga.)
There were no specific reamers for specific final choke diameters; the reamer was simply pushed further into the bore until the desired diameter was achieved. With this collection, I also obtained the rods which the reamers were screwed to. These rods have adjustable stops, which allowed the breach face to only move so far in relation to the reamer. The length of taper, logically, for a full choke was close to the full length of the reamer, however, a choke considerable more open would have a uniformly shorter taper.
I do not believe there is any data which supports the belief that there was a "Standard" length of taper. As reamers required sharpening, they were ground, on offset centers, and, consequently the length of the cutting portion, at a specific diameter, would become shorter over the life of the reamer. These tools were likely the property of the individual tradesman, and they may have seen many regrinding cycles. Today, the reamer would simply get tossed to the scrap barrel, and operator would take a new one out of the tool room.

Neet stuff Edgar. What centered the reamer I've reamed bushings but they weren't tapered. Impressive the craftsmanship those fellows had. What did they take the reamer marks out with, a stone hone?

Is this correct or should it be eliminated?
http://www.parkerguns.org/pages/faq/ChokeSize.htm

That's a good question Calvin.
The barrel tubes had been rough bored, prior to the choke reaming. The term 'rough' didn't suggest it was a coarse cut, or unsmooth surface, it merely differentiated the operation from a final polish.
The bore was then given an operation, taking it down to 'near-bore' dimension (varied from early guns of slightly over .750" to late guns closer to today's .729") The last few inches were finished with the choke reamer.
The flights (or flutes) of the reamer wanted to resist cutting into the barrel wall, and naturally sought to move off the wall, toward center. As all the other flights were doing the same thing; seeking a balance in concentricity, the reamer stayed in the geometric center of the tube.
The Sunnen hone, much like a brake cylinder hone, except on a long shaft, with a hollow center allowing cutting oil to flood the area, also stayed centralized in the same manner.
Variation in barrel wall measurements are almost always a result of 'striking' the outside surface of the barrel; the operation of prepping the barrel for final finish.

Robin, those figures have been the standard for years and should not be eliminated. Just my $.02.

Edgar, that is some really neat stuff.

I guess I should have stated that with this gauge, you zero out the dial using the supplied .700 diameter ring, then when placed in the barrel it read .051, so effectively .751 as a starting point.

Bob, it took me a moment or two to understand your table of figures, but now I see what you were saying.you have a difference between the bore of .751, and the muzzle of .722, giving you .029" constriction. It depends on whose chart you read, but it's certainly closing in on full.
My only question is your table doesn't seem linear, and looks like it bells in the last inch or so.
All of my Parker choke reamers are very straight. (but tapered, duh)

That's what I'm concerned with, that much constriction in the last inch or so. Doesn't seem right to me?

That chart is on the money. That said, I think every gun should be pattern tested with whatever load you will be using.

I wish I could understand all that machinist mumbo jumbo but I don't. I always considered .030 as the start of the full choke range but the patterning board results are what really count.

Edgar, with a straight line (tapered) cutter how did they arrive at the 'ogee' at the beginning and at the end of the length of the choke taper? Was the ogee the result of the final hone and polish?

I recall reading that Parkers produced in Illion did not have the ogee that the Parker Bros. craftsmen finished the chokes with... I wonder why not and if the transition from the cylinder tube directly to the choke cone would affect the pattern by the possibility of more shot pellets being deformed?

I have a 12 bore with .041" and .042" of constriction that is certainly tighter than the .029" constriction suggested as full choke... so, what degree of choke should I call it?





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that is where my Elsie Longrange is - I think Super Foxes are typically around that or even just a bit more

i just call it extra full

Incidentally, this is the gun that Larry Frey used to win the New Year's Day Shoot with. It reaches out there.





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A straight tapered reamer is not going to yield anything but a straight taper. Any machining operation that yielded a curved surface at either end of the taper was either done by a hand lapping operation, or another tool. Of all the reamers in Hayes' tool box, there are no such reamers.

I Can't comment on this, because I have never read what you're refering to, nor do I own, or care to own , any Ilion Remington made Parkers

Cheerio tight. Not a British choke term, but a Yankee one, describing a gun so tight, you can shoot through a Cheerio and not break it.

My Fox Sterlingworth is .044" in both barrels. I believe it will shoot 1" groups at 100 yards

The "chart" does not mention that the bore diameters listed are nominal dimensions and, for example, about half of the Parker production was not bored to those dimensions. Some comment should be made about early Parkers, Super Foxes, German guns and many other examples that do not conform to the .729 standard.

Bill, I don't know if I'm reading you right, but it doesn't matter [ within reason ] if the bore is .725 to .750, it's the amount of constriction that dictates choke. I have a chart hanging on the wall over at the club from some screw in choke manufacture that is a bit easier to remember.
SK - .005
IC - .010
SKll or LM - .015
Mod - .020
IMod - .025
Full - .030
Everything is linear and in MHO as is should be.

[QUOTE=Dean Romig;210030]
I have a 12 bore with .041" and .042" of constriction that is certainly tighter than the .029" constriction suggested as full choke... so, what degree of choke should I call it?

Deanno, according to my Shotgunner's Urban Dictionary that's listed as: MFT.

Just text your local Millenial for a more accurate definition.....:whistle::bigbye:

:shock: Does the T represent Tight??:shock:





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I think we all know what the "F" is

And my 20ga. Sterly is .035. MFT.:eek:

I have a 12ga parker 26" vr bbl choked out at 021/023.
is this common?

Wow... I wonder what that gun was ordered for?




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