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bore diameter
- Thread starter Newton24b
- Start date
Jim Watson
New member
Colt and Remington percussion revolvers were normally referred to as .44 caliber, not .45.
But caliber designations are only nominal and sometimes it is hard to find an actual measurement in the gun that agrees with the number in the book.
But caliber designations are only nominal and sometimes it is hard to find an actual measurement in the gun that agrees with the number in the book.
This may veer off topic, but I think that the best example of a caliber not matching bore diameter is the .38 Special.
The .38 Short Colt was used in old .36 caliber pistols. The .38 Short used a heeled bullet, so the exposed portion of the bullet was the same diameter as the case - about .375".
The .38 Long Colt didn't use a heeled bullet, but the case diameter was the same as the .38 Short. And the .38 Special was derived from the .38 Long, so the naming convention stuck.
The .38 Short Colt was used in old .36 caliber pistols. The .38 Short used a heeled bullet, so the exposed portion of the bullet was the same diameter as the case - about .375".
The .38 Long Colt didn't use a heeled bullet, but the case diameter was the same as the .38 Short. And the .38 Special was derived from the .38 Long, so the naming convention stuck.
Someone correct me if I'm wrong but as I recall....
In the USA, generally, the bore of a handgun in measured between the lands whereas the bore of a rifle is measure between the grooves.
For example, on a Ruger Old Army, typical dimensions are:
Lands Diameter: 0.443"
Groove Diameter: 0.451"
Chamber Diameter: 0.453"
So, on an ROA we see that the recommended 0.457 roundball get shaved down to 0.453 when seated in the chamber. The roundball remains .45 caliber. When fired, the shaved roundball gets squished down to 0.451 when pushed through the forcing cone. The roundball remains .45 caliber. However, since the lands diameter is 0.443 this firearm is designated a .44 caliber. Confusion persists on this topic when a firearm like this is converted to shoot .45 Colt cartridges since the typical bullet diameter used is 0.452.
Recall, that some ROAs left the factory marked ".44 caliber" and while others were marked ".45 caliber". Both of these revolvers are identical. The only difference are revolver's markings for caliber. I believe, from a technical point of view, both markings are correct. It was just a marketing ploy by Ruger to get a .45 caliber classification for a USA measured .44 caliber revolver. I believe the ATF would consider the ROA to be .44 caliber. However, I seem to recall that Ruger may have marked some ROAs as .45 caliber to get acceptance of these firearms in other countries which use the groove diameter consistently for all firearms regardless of if it's a rifle or handgun. Great Britain comes to mind. Additionally, from the point of hunting statutes in some states, I believe there is a legal advantage for hunting purposes when the desire is to hunt with a handgun. I don't hunt so I don't know the specifics.
So, as you can see, it depends on how you want to measure the bore...lands or grooves...
In the USA, generally, the bore of a handgun in measured between the lands whereas the bore of a rifle is measure between the grooves.
For example, on a Ruger Old Army, typical dimensions are:
Lands Diameter: 0.443"
Groove Diameter: 0.451"
Chamber Diameter: 0.453"
So, on an ROA we see that the recommended 0.457 roundball get shaved down to 0.453 when seated in the chamber. The roundball remains .45 caliber. When fired, the shaved roundball gets squished down to 0.451 when pushed through the forcing cone. The roundball remains .45 caliber. However, since the lands diameter is 0.443 this firearm is designated a .44 caliber. Confusion persists on this topic when a firearm like this is converted to shoot .45 Colt cartridges since the typical bullet diameter used is 0.452.
Recall, that some ROAs left the factory marked ".44 caliber" and while others were marked ".45 caliber". Both of these revolvers are identical. The only difference are revolver's markings for caliber. I believe, from a technical point of view, both markings are correct. It was just a marketing ploy by Ruger to get a .45 caliber classification for a USA measured .44 caliber revolver. I believe the ATF would consider the ROA to be .44 caliber. However, I seem to recall that Ruger may have marked some ROAs as .45 caliber to get acceptance of these firearms in other countries which use the groove diameter consistently for all firearms regardless of if it's a rifle or handgun. Great Britain comes to mind. Additionally, from the point of hunting statutes in some states, I believe there is a legal advantage for hunting purposes when the desire is to hunt with a handgun. I don't hunt so I don't know the specifics.
So, as you can see, it depends on how you want to measure the bore...lands or grooves...