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choke size


milo2005
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Milo, hi,

Got a feeling this one is going to be fun.

You cannot accurately measure choke unless you know the main barrel diameter. However, if you assume (always dangerous) that the gun has not been got at then you can use the nominal barrel dia. For a 12 bore this is 0.729". Using a vernier caliper to measure the muzzle dia. will give a ball park answer. Having said that, no matter what degree of sophisticated measuring equipment you use all you will get is a dimension which may well have no bearing on how the gun shoots. The be all and end all is to pattern it.

Cheers

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No not at all,

 

A gauge will only work if it designed to suit your barrels bore. Baikals always used to be .729" bore when I worked on them so you should be able to deduce what choke is in each barrel by using a vernier.

 

The bore diameter should be stamped on the proof marks.

 

Assuming your bore is .729" then

 

cylinder would be .729" at the muzzle

1/4 would be .719"

1/2 would be .709"

3/4 would be .699"

full would be .689"

 

If the barrel is full length and has not been shortened it should have a criss cross pattern on the muzzle.

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The stamps along side that are the manufactured sizes, you had half in the bottome barrel and full in the top which is how all baikals came in to the country. The were there altered by cutting a certain ammount off the barrel.

 

It was a long time ago when I used to do it but I think that 27 5/8" from the breech gave 1/4 and 1/2 and 27 3/8 gave cyl and 1/4.

 

18.3 is the bore in millimeters which equates to .720" so if you take .009 off the measurements that will give you a rough guide.

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Hi, again,

Getting confused? MC's figures are good. I think you are talking about a choke gauge. The datum for these is the nominal bore diameter. So, if you're measuring a 12 bore with a 12 bore gauge all will be well provided your barrel is that nominal diamension. However my remarks about patterning are good.

Good luck.

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hi,

You and MC posted while I was typing. There we go cracked it! If you can get access to a vernier you will get a more accurate answer but the gauge will do. However, with the gauge you will have take the next lowest choke level to what the gauge tells you: eg gauge 3/4 your barrel is 1/2. It works because full, 3/4, 1/2 and 1/4 chokes are all 0.010" in difference and you need to deduct, as MC says, 0.009". What's a thou among friends!

Cheers

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hi,

You and MC posted while I was typing. There we go cracked it! If you can get access to a vernier you will get a more accurate answer but the gauge will do. However, with the gauge you will have take the next lowest choke level to what the gauge tells you: eg gauge 3/4 your barrel is 1/2. It works because full, 3/4, 1/2 and 1/4 chokes are all 0.010" in difference and you need to deduct, as MC says, 0.009". What's a thou among friends!

Cheers

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The only reason I said .009 is because his barrel is 18.3mm which is .720 not .729.

 

I am not an engineer working to the nearest thou, I am a joiner and we like to be exact :good:

 

If your barrel is 27 1/2" then chances are it has been cut down as I am certain they were 28 1/2" from the factory.

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Milo,

 

That is correct as long as your barrels haven't been altered. ALL Baikals came from Russia with 1/2 and full chokes. They were altered in the Sportsmarketing factory in Colchester where I worked for a couple years after leaving school.

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Just purchased a bore meausuring tool from Brownells in the USA, based on a DTI gauge, stem is about 14 inches long.

 

The only way to accurately measure choke (in comparison with standard bore size) is to get measuring.

 

If you were in Lancashire I would measure it for you.

 

I think the Baikal method off chopping down the barrel only works when the choke is tapered. The ones I have measured seem to be parallel after the forcing cones

 

Cheers Dave

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Hi, Milo,

Oops! Before I comment, I'm sure you meant 1/2 in the bottom. As I said earlier, the be all and end all is to pattern the gun but there's two things you could do before going to that trouble. Pop in to your local dealer and get him to run his barrel DTI through it. This will immediately give you the mean barrel dia. and the choke dia. This will give you your nominal degree of choke. It will also give you your choke profile, ie, tapered or the usual cone/parallel. Also you could do a quick pattern spread test. From 20 yards and from previously fired barrels fire several shots at suitable targets (cardboard or whatever). Ignoring any obvious flyers, measure the spread dia. and take the average for each barrel.

TC is32",IC is26" 1/4 is 23" 1/2 is 21" 3/4 is 18" and FULL is 16"

Cheers and good luck

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