Choke size in thousands of an inch ( Help )

[figgy]

Do what they used to do years ago. Get some different cartridges and different size loads and pellets, shoot them see what patterns and at what distances then choose the cartridge to suit what your needs are.

 

You might find a 32g 5shot patterns well to a good distance and a 28g 5shot opens more but is a good close range cart. Change your cart like folk would change chokes.

[FalconFN]

I think I know what you mean..

Just can not figure out how to measure 9" behind the choke.

Hmmmm, I will have to work that one out...LOL

Only got Digital Vernier's

If you have a gunsmith nearby they will have a measuring tool. I was in a similar position recently and it is useful to know, but as others have said the pattern with different cartridges is more important.

[old'un]

I would agree with Stonepark from the figures you have given i would say somewhere between improved cylinder and quarter choke,
but if you must put figures to your barrels then you need a barrel mic (most gunsmiths have these)
take a measurement about 9 inches from the muzzle and one at the muzzle, take one figure from the other and look at your chart to find roughly what choke is in each barrel,
although there are lots of other influences that can effect how you gun patterns/shoots.

[fortune]

 

Ok - so you sound like you want the complicated version.

First, the constrictions themselves:

On the basis that Baikals are pretty much indestructible and that you haven't said the bores of the gun are rusted / pitted, we'll assume the markings of .719" on the gun are correct. I've owned two Baikals so far and the marks have been spot on both times. That means you've got constrictions of 0.008" in the .711" barrel and 0.006" in the .713" barrel.

Next, the classification system:

There are several ways of classifying the "choke" a gun has. Broadly, these are the American system based on constrictions, the traditional English system based on constrictions, or the "true" system based on patterns and pellet counts.

Briefly:

• the American system, which labels chokes things like "improved modified" and "skeet II" specifies constrictions for each kind of choke (half, full, etc.) proportional to the bore of the gun. A half-choke constriction in a 12 gauge is a greater absolute constriction than a half-choke constriction in a .410.
• the traditional British / English system which labels chokes as "quarter", "half" is much less used nowadays, though some of the Turkish manufacturers have adopted it. It specifies that a half-choke constriction is always 0.020", irrespective of bore diameter.
• the "performance" system is achieved by cutting open a number of cartridges, counting the pellets and then shooting more of the same cartridges at pattern plates, finding the centre and counting the number of pellets which fall within a standard 30" circle at any given distance. This gives you a choke performance expressed as a percentage, for that cartridge and that choke at that range, which can then be converted into a label - "full" (typically 70%), "half" (typically 60%), "improved cylinder" (typically 50-55% - depends if people equate it with "quarter" or not) - whichever label from which ever system you think describes it best, though expressing it as a percentage is always clearer.

The first two systems are approximations. They're more useful to people selling guns than people using them, because customers will have an idea of what chokings they want and will think that if they buy something labelled "quarter and half" that they've got what they want, even if the patterns it throws with their cartridge are nothing like quarter and half patterns.

So, under the American system, you have a gun with chokes which are both in the range between what they call "skeet" and "improved cylinder".

Under the British system, you have a gun with chokes which are both in the range between what we call "cylinder" and "quarter" chokes.

I suspect that the American system (choke constriction proportional to the bore diameter) probably better reflects, in general, the way that shotguns perform. However, there are so many exceptions to the rule that you should treat this as the vaguest indicator, rather than a hard and fast statement of fact.

Note also that you can't necessarily convert between the American or English constriction classification systems unless you know whether you're comparing constrictions or choke performance expressed as a percentage.

Imagine a gun throwing a 70% pattern in the 30" at 40 yards. Under the "performance" system, it has a full choke with that cartridge, no matter how many notches, stars or other labels are on the choke or where it came from or what the constrictions are. With this measurement, you can have a reasonable expectation of how the gun will perform.

Consider though that a 28-gauge gun with a 0.020" choke constriction which throws the above pattern would still be labelled "[light] full" in the US and "half" in the UK. Likewise, a 12 gauge gun with a 0.020" choke constriction which throws the above pattern would be labelled "modified" in the US and "half" in the UK. All of these labels are meaningless, except to indicate the constriction of the choke, which tells you nothing about how it will throw the shot. If it throws 70%+ of the shot at the standard pattern at the standard distance, it's full-choked, no matter what it says.

As for what your gun actually does, you will only know by patterning it. Here are some of the guns I have or have had in the past:

• a semi-automatic which throws tighter patterns through a choke labelled "Modified" than a "Full" choke with my normal game cartridge.
• a 28 gauge which has chokes labelled under the English system "quarter and half". It shoots 68% and 75% patterns respectively, which are "improved modified" and "extra full" under the "performance" system. Interestingly, if you translate the constrictions on the gun to the American system, they come out at "light modified" and "light full", ergo none of the possible labels based on constrictions reflect the gun's performance (with that cartridge).
• a 16 gauge choked 3 stars ("half") and one star ("full"), which throws 72% ("full") and 78% ("extra-full-and-then-some") patterns with my standard cartridge.
• a .410 choked "full" which threw 50% ("quarter") patterns - the combination of over-choking and long shot column damaged so many pellets that the pattern was consistently "blown".

In short, your only option is to become an honorary member of the CCPS, get out there and shoot some cardboard boxes!

Adam.

​

Edit

Here are some links to help with the above.

American Constrictions System: http://www.briley.com/c-448-bore-sizes-and-constrictions.aspx

English Constrictions System: http://www.purdey.com/Global/Images/pdfs/Choke_Chart1.pdf

"Performance" System: Chart 1 at http://www.wildfowlmag.com/tactics/tips_strategies_shotgun_062304/for one of the many examples.

​

 

 

That is a good read. really informative.

BUT when you go through all of that. >>>By the time that you mess about with all of that and blast off a load of lead. you can find some stamps and mark it up with whatever takes your fancy, in fact you could stamp it up with several different chokings depending on what system is used you could have been out shooting loads of what target you shoot. So my previous comment still stands

 

Nah, just shoot the blighter.

 

[Fieldsports]

I have had the gun out today, with the full intention of doing a pattern test BUT
Literally 20 ft away from where I parked the dog put some very sporting pheasants up at a good old distance and then we hunted some reshy beds out and low and behold I was suddenly filling my bag with some nice birds and rabbits.
This excitement went on for quite some time until I remembered why I went out today ( To pattern test the gun ) LOL
Well will have to do it another day now as I have had a busy night skinning and preparing the game for my renowned game stew and a coupe of Rabbit and black pudding pies.
One of them days when my plan went wrong all for the right reasons.
Maybe I will just take an educated guess with the choke sizes ! It is shooting like a dream and I can hit my quarry superb, so I might just put up with what it is...LOL
After all it seems to work good for me what ever the size of the chokes are.

[Chris Bb]

After all it seems to work good for me what ever the size of the chokes are.

 

And that, when everything else is considered, is what it's all about!