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Actual choke measurement


stu64
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I'm going to try to keep this short. I bought a secondhand marocchi from a dealer and with it came two new teague chokes- quarter and half.( it uses classic doubles chokes). it also had original full and cylinder chokes.I wanted either another quarter or skeet choke so I thought i would measure the original cylinder choke to make sure it was cylinder. Barrels are stamped 18.5 which is 0.728", the choke measured at 0.729 so good enough for me. Then i thought i would measure the teague chokes-don't know why- but the half measured 0.704 and the quarter measured 0.714. Going by teagues choke chart this means the half choke is actually 5/8 and the quarter is actually 3/8. The original full choke measures 0.686 which is within 2 though of being spot on. Apart from thinking teague chokes would be more accurate than this I'm not sure there's much else to say. I did order a skeet choke at 5 thou constriction and wait to see if it ends up being skeet or quarter. I've used the gun twice on clays with cylinder and quarter fitted-it shot fine-I haven't patterned it but may well just out of curiosity.

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2 minutes ago, stu64 said:

absolutely agree with you. I'll see what the new skeet choke measures up at to see if teague are consistent.

I have quite a few slimline teagues, including both 3/8ths and 5/8ths, but they’re actually marked as such, so perhaps it is simply a matter of method used? 

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13 minutes ago, TIGHTCHOKE said:

Measure the internal diameter of the barrel, measure the choke, workout the difference and then it is one point of choke for each 10"thou tighter constriction.

Know what TC means, but some could be confused as "one point of choke" in gunsmiths' terms is 0.001" of choke. If it helps, every Teague choke that I've had experience of has shot 1/8th more open than specified. If the OP does pattern them properly, it would be interesting to see if they do throw 1/4 by 1/2.

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The barrel is stamped 18.5mm and this is the figure quoted on teagues website for that gun, used as their reference. according to teagues own choke chart each choke reduces diameter by a further 5 thou. It maybe that the chokes I have are mis-labelled-who knows. As I say, when the skeet choke arrives I'll measure that just to see.

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Until you actually measure the bore size, as has been said, the 18.5mm is only the proof size which will vary within the proof parameters. In old money my Baikals are marked .019" which simply means that a .019" plug gauge will go in but a .029 will not so the bore size could be anywhere in between. Nowadays there is an intermediate size so the possible variation is less. It does all get like counting angels on the head of a pin, and that's without considering the varying patterns of different cartridges. Just shoot it !!

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I understand what you are saying, but my point is teague's choke measurements don't agree with what teague themselves put on their website. Teague use 18.5mm as their reference/starting point and each goes down 5 thou. I'm not particularly bothered that they don't tally up, I just thought teague would be more accurate thats all.

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Get a large piece of paper and a tape measure.

Fire a cartridge and photograph the result.

Change the paper and repeat 9 more times.

Now count up the strikes and get your calculator out.

Work out the average and you have a fair indication of what that barrel, choke and cartridge are throwing.

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Surely 18.5mm is the nominal internal dimension at the 9" from the breech WHEN THE GUN WAS PROOFED and bears absolutely no direct relationship to the diameter internally of the barrel just before the choke constriction? The correct way to measure choke is to subtract that dimension (just before the constriction) from the choke constriction and the answer is the degree of choke that you have subject to the individual foibles of the gun and the actual cartridge used as the only true way to determine an exact actual result is to shoot the gun on a plate and see what pattern it makes.

11 minutes ago, TIGHTCHOKE said:

Get a large piece of paper and a tape measure.

Fire a cartridge and photograph the result.

Change the paper and repeat 9 more times.

Now count up the strikes and get your calculator out.

Work out the average and you have a fair indication of what that barrel, choke and cartridge are throwing.

This.

Edited by enfieldspares
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Stu,

 

Patterns (and choke) are all measured on the pattern plate by counting number of pellets in 30 inch circle compared to how many started off in the cartridge, the empirical measurements of bore diameter and choke diameter are only ever a guide due the variables of their relationship and cartridge choice.

 

As per the above, checking what the results are will be the only way to confirm if it is throwing the patterns that you are looking for, even though the empirical measurements may be 'wrong' the patterns thrown may be better or worse and until checked, any thing else is just a guess.

 

I normally pattern new chokes with a high (5%) antimony fibre clay load for consistency.

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