I've bought a few original and older repro ML smoothbores recently and the title of this thread has been a contested point of fact in each. I'm not trying to give a full lesson nor preach, just provide a general clarification. You can use the information any way you deem appropriate or disregard it altogether.
Gauge is not a numerical linear measurement. Gauge is the # of balls that are full-sized to fit in the bore and equal a pound.
Bore is the linear measurement of the inside diameter of the barrel measured in front of the breach.
Choke is the difference in the inside diameter of the barrel and the tightest point of constriction, usually at the muzzle (yeah-yeah there can be a jug choke before the muzzle).
The English and one French ML smoothbore I just got have the bore diameter expressed in inches, stamped on the barrel(s). A Spanish and Italian smoothbore respectively have the bore diameter expressed in millimeters.
The next piece of information to put this all together is what is a "standard diameter". In other words what diameter bore sized lead balls in a certain quantity equal a pound? 12-gauge should have 12 equal balls that are bore diameter weight one pound. There is slight variation in lead composition, altitude, and other minor factors that will vary weight slightly, but a generality is that .729 or .730-inch is a 12-gauge.
So, you need to be able to measure the inside barrel in front of the breach to get that #. If you do not have the capability of measuring there, you can choose to trust the markings on the gun.
Here's an example of two I purchased and how this all ties in:
Advertised as a 12-gauge with Modified chokes, this gun has 18.2mm marked on the barrel. The muzzle measures 0.717-inch. Well, 0.717-inch is 18.2-mm. So, first of all this gun is not a true 12-gauge. 12 lead balls of .717-inch weigh less than a pound. I'm not doing the math here, but maybe it's a 13-gauge or a 12.75 gauge but the "gauge" is rounded to a whole #. Second, this gun has zero choke. The bore diameter is the same as the diameter at the muzzle. (I know there could be a jug choke before the muzzle but in this case, there is not).
Advertised as a 12-gauge with Full chokes, this gun has 18.4mm bores. That's .724-inch. So, it's not quite a true 12-gauge to the "standard" but pretty close (.005 smaller). The muzzle inside diameter measures .708-inch. So this gun does have some choke, in fact .016-inches of it compared to the .724- bore. However, that is not "Full choke" to the standard. .716 would ordinarily be considered IC in a "standard" .729 12-gauge but in this case the amount of constriction compared to the bore diameter make the choke "name" Light Modified.
Advertised as a 20-gauge with Full chokes: I will spare you the details and boredom by simply saying this is actually a 24-gauge with Cylinder bores, or no choke.
Now, there's another whole matter and that is performance application. The measurements and names for constriction are great points of reference and when expressed properly are helpful for a user/buyer to determine what the gun's starting point is. But it is how the barrel patterns the shot within the standards that really define the choke by name. The standard is to shoot a static pattern at 40-yards and define the number of pellets in a 30-inch circle by a percentage of the total # of pellets that you started with in the barrel. With a muzzleloader in particular, the way you load the gun and with what can make a huge difference in the patterns name compared to what the bore to constriction diameter indicates.
After firing 10-shots for each of the above guns, and carefully determining the # of pellets in the pattern and converting to a percentage I determined the following: None of them throw a pattern that would match the name given to the amount of constriction precisely.
Conclusion is that you have to know how to measure what and where, and how to categorize the findings. By doing that you can determine the gauge in whole #'s, the numeric amount of constriction and the "name" for that amount of choke. But only by pattering the gun can you determine the practical performance of any choke or the lack thereof.
I hope this is helpful to someone.
Gauge is not a numerical linear measurement. Gauge is the # of balls that are full-sized to fit in the bore and equal a pound.
Bore is the linear measurement of the inside diameter of the barrel measured in front of the breach.
Choke is the difference in the inside diameter of the barrel and the tightest point of constriction, usually at the muzzle (yeah-yeah there can be a jug choke before the muzzle).
The English and one French ML smoothbore I just got have the bore diameter expressed in inches, stamped on the barrel(s). A Spanish and Italian smoothbore respectively have the bore diameter expressed in millimeters.
The next piece of information to put this all together is what is a "standard diameter". In other words what diameter bore sized lead balls in a certain quantity equal a pound? 12-gauge should have 12 equal balls that are bore diameter weight one pound. There is slight variation in lead composition, altitude, and other minor factors that will vary weight slightly, but a generality is that .729 or .730-inch is a 12-gauge.
So, you need to be able to measure the inside barrel in front of the breach to get that #. If you do not have the capability of measuring there, you can choose to trust the markings on the gun.
Here's an example of two I purchased and how this all ties in:
Advertised as a 12-gauge with Modified chokes, this gun has 18.2mm marked on the barrel. The muzzle measures 0.717-inch. Well, 0.717-inch is 18.2-mm. So, first of all this gun is not a true 12-gauge. 12 lead balls of .717-inch weigh less than a pound. I'm not doing the math here, but maybe it's a 13-gauge or a 12.75 gauge but the "gauge" is rounded to a whole #. Second, this gun has zero choke. The bore diameter is the same as the diameter at the muzzle. (I know there could be a jug choke before the muzzle but in this case, there is not).
Advertised as a 12-gauge with Full chokes, this gun has 18.4mm bores. That's .724-inch. So, it's not quite a true 12-gauge to the "standard" but pretty close (.005 smaller). The muzzle inside diameter measures .708-inch. So this gun does have some choke, in fact .016-inches of it compared to the .724- bore. However, that is not "Full choke" to the standard. .716 would ordinarily be considered IC in a "standard" .729 12-gauge but in this case the amount of constriction compared to the bore diameter make the choke "name" Light Modified.
Advertised as a 20-gauge with Full chokes: I will spare you the details and boredom by simply saying this is actually a 24-gauge with Cylinder bores, or no choke.
Now, there's another whole matter and that is performance application. The measurements and names for constriction are great points of reference and when expressed properly are helpful for a user/buyer to determine what the gun's starting point is. But it is how the barrel patterns the shot within the standards that really define the choke by name. The standard is to shoot a static pattern at 40-yards and define the number of pellets in a 30-inch circle by a percentage of the total # of pellets that you started with in the barrel. With a muzzleloader in particular, the way you load the gun and with what can make a huge difference in the patterns name compared to what the bore to constriction diameter indicates.
After firing 10-shots for each of the above guns, and carefully determining the # of pellets in the pattern and converting to a percentage I determined the following: None of them throw a pattern that would match the name given to the amount of constriction precisely.
Conclusion is that you have to know how to measure what and where, and how to categorize the findings. By doing that you can determine the gauge in whole #'s, the numeric amount of constriction and the "name" for that amount of choke. But only by pattering the gun can you determine the practical performance of any choke or the lack thereof.
I hope this is helpful to someone.
