Question on vintage choke markings

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gunsaholic

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I have a Belgian gun here from 1930 that I'm trying to decipher the chokes on going by the proof markings. Now I have been told in the past that when there is only one number stamped in the barrels it usually refers to the bore size and if there are 2 numbers one is bore and the other is muzzle measurement. This gun has the stamping 18.3choke18.2. Both barrels are stamped the same. 18.3 equates to .720, a fairly tight 12 gauge. 18.2 equates to .716 which is indicating a .004 constriction which is skeet/skeet. The thing is, I don't get anywhere near that .716 at the muzzles when measuring with my digital caliper. I get .690 in one barrel and .684 in the other. Looking at the readings manually, it's pretty close to what it's saying digitally. Am I wrong in understanding what the 18.3choke18.2 means or are both numbers just indicating nominal bore size?
 
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The 18.3 would be the bore size not the choke size. My Perazzi MX8 has a 18.4 sized barrel choked fixed full on top and a removable choke on the bottom. If I remember correctly the full choke is .690 or so. I would say you gun has a 18.3 barrel and a 18.2 barrel choked full and improved modified or full and full although they don't usually use that terminology in Europe.

Edit: I had to check bUT a full choke is considered a 0.030 constriction so your 0.720 - 0.030 = 0.690.
 
I also have an older Belgian box lock it is a Verrees & Oste Manufactured I believe in 1949 a few years before they purchased Lebeau Courally. It has 70mm chambers and the barrels are similarly stamped with the first barrel being stamped 18.5 choke 18.3 and the other stamped 18.5 choke 18.2 so would not the bores size be 18.5 and chokes 18.3 and 18.2 ?
 
silent said:
I also have an older Belgian box lock it is a Verrees & Oste Manufactured I believe in 1949 a few years before they purchased Lebeau Courally. It has 70mm chambers and the barrels are similarly stamped with the first barrel being stamped 18.5 choke 18.3 and the other stamped 18.5 choke 18.2 so would not the bores size be 18.5 and chokes 18.3 and 18.2 ?
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That is what I was thinking with mine, the bore being 18.3 and the choke 18.2. However, measurements at the muzzle do not bear that out. It is more likely that both numbers are bore measurements at various spots of the barrels. As mentioned by bdft, subtracting the choke size of 0.030" from .720 (the bore size) gives the number that my measurements at the muzzles give me.
 
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I see what you are saying as your barrels are both stamped the same I believe, But if that is the case with mine the measurements are different for each barrel and would indicate a different bore diameter for each barrel and wouldn't the bores match normally? I don't have a set of callipers to measure at the muzzle or I would. I am a bit new to doubles but enjoy researching the few I have.
 
gunsaholic said:
I don't think it was uncommon back in the day to see barrels that had different measurements from one another.
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Your correct but I don't think it was necessarily done on purpose unlike today where it is not uncommon for Olympic doubles trap shooters to order one barrel of a different bore diameter than the other believing that one bore is better than another for the different distances.
 
gunsaholic said:
That is what I was thinking with mine, the bore being 18.3 and the choke 18.2. However, measurements at the muzzle do not bear that out. It is more likely that both numbers are bore measurements at various spots of the barrels. As mentioned by bdft, subtracting the choke size of 0.030" from .720 (the bore size) gives the number that my measurements at the muzzles give me.
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Not skeet IMO
http://www.hallowellco.com/choke_chart.htm
 
Choke is the amount of constriction of the barrel at the muzzle. To know this figure you must first know the actual bore size and the actual muzzle size. Then you subtract the muzzle size from the bore size and you will get the measurement of the actual amount of choke. You can apply this measurement against a table ( all choke manufacturers have them on their website.) if you want to give this measurement a name such as full ( ie .035" of choke = full). You can not tell the true amount of choke without having BOTH of these measurements, one (such as muzzle diameter) isn't enough. On an older gun with unknown history you can't rely on the original markings to tell you what the chokes are now because the bores may have been honed to remove pitting or the chokes opened up, these markings only show the dimensions when the gun was manufactured. A shotgun barrel bore gauge is required to accurately measure the bores, some gunsmiths have them.
 
Ashcroft said:
Choke is the amount of constriction of the barrel at the muzzle. To know this figure you must first know the actual bore size and the actual muzzle size. Then you subtract the muzzle size from the bore size and you will get the measurement of the actual amount of choke. You can apply this measurement against a table ( all choke manufacturers have them on their website.) if you want to give this measurement a name such as full ( ie .035" of choke = full). You can not tell the true amount of choke without having BOTH of these measurements, one (such as muzzle diameter) isn't enough. On an older gun with unknown history you can't rely on the original markings to tell you what the chokes are now because the bores may have been honed to remove pitting or the chokes opened up, these markings only show the dimensions when the gun was manufactured. A shotgun barrel bore gauge is required to accurately measure the bores, some gunsmiths have them.
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Yes, I am aware of what you are saying but I was just trying to determine what the markings indicated as I was told before that if there are 2 numbers, then one is the muzzle dimensions at the time the gun was made. Since this does not bear out with actual measurements, I was wondering really what the 2 sets of numbers mean. I know chokes can be opened up or bores honed/reamed which would make factory markings useless. In my case, the muzzles are tighter, not more open than what the 18.2 indicates so I was wondering what it signifies. I just asked on another forum and below is the answer I was given.

Has been a while since I looked up Belgian proof marks, but as I recall the 18.3 & 18.2 are bore diameters. Most likely taken before & after final polishing. Thus at final proof, it would have had the 18.3 (.720") bores. The word choke as I recall means that barrel has at least, but not limited to, 0.2 mm (.008") of choke. The choke should now read 18.1 mm (.712") or smaller
 
Depending on the vintage of the Belgian gun the two numbers are what the bore diameter was at provisional proof time testing and what they were when the bore went through final proof when it was finished. Hence the smaller number is the bore measurement before it was polished finished whatever you w ant to call it. The larger number is the actual bore diameter of the finished gun. Also depending on the vintage the word choke will be stamped as well. This means the barrel is choked. The numbers do not tell you the degree of choke. Measure the muzzle diameter and subtract it from the smaller number 18.2 in your case and you will be close to the choke amount. Obviously the 18.2 is metric. Shooting it at a pattern board will tell you actual choke. Remember those guns were not designed to pattern with shot collars. Oops as noted on previous response I have the numbers reversed 18.3 is the larger final bore diameter but I'm not sure if it is right before the choke which is the only bore diameter which effect choke.
 
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