True bore diameter

Hello,
Knowing that one of the most important factors in accuracy is having the proper bullet diameter to bore diameter fit, I picked up a caliper to check the bore diameter of my A & H Hawkens. The question I have, do I want to measure from top of the land to top of the land, or bottom of the groove to bottom of the groove. Which is the correct bore diameter measurement.

Thank you,
Blacky Montana
SASS #19953

Blacky Montana said:

Hello,
Knowing that one of the most important factors in accuracy is having the proper bullet diameter to bore diameter fit, I picked up a caliper to check the bore diameter of my A & H Hawkens. The question I have, do I want to measure from top of the land to top of the land, or bottom of the groove to bottom of the groove. Which is the correct bore diameter measurement.
Thank you,
Blacky Montana
SASS #19953

Click to expand...

A bore is the center "bored out" part of a barrel.
Then some grooves are cut into the metal.
The raised surfaces called lands are still at the original "bored" diameter.
Measure from land to land to get bore diameter.

Actual Example:
I bought a GM .62cal smoothbore barrel (bore was .610")
Then I had a barrel maker cut grooves into it...the remaining lands still represent the original .610" bore diameter...grooves are deeper of course.

RB, that is how we measure a bore here in America, but Europeans do it differently. They measure to the groove depth. That is why people get messed up when they find a nice milsurp rifle, like my Swede M38 or Swiss K31 and try to figure out a bullet to use. The Swiss 7.5x55 uses a .308 bullet, and the Swede 6.5x55 uses a .264 bullet.
I have no idea if the European muzzleloaders do this also, but that system has confused many people.

Jim

Didn't know he was from Europe asking about a European muzzleloader...but my answer is still the same :grin:

I don't know if he is from Europe either. I was just dipping a little into the vast sea of my knowledge and sharing with the mere mortals who frequent here. :grin:

Jim

pepperbelly said:

I don't know if he is from Europe either. I was just dipping a little into the vast sea of my knowledge and sharing with the mere mortals who frequent here. :grin:

Jim

Click to expand...

Shazam! :rotf:

pepperbelly said:

I don't know if he is from Europe either. I was just dipping a little into the vast sea of my knowledge and sharing with the mere mortals who frequent here. :grin:

Jim

Click to expand...

...or...you've been hangin around with Rebel too much out there ! :grin:

The BORE is LAND TO LAND regardless of your location. If your in Europe and measure from groove to groove, you will not have measured the bore, you will have measured the groove diameter.
Metallic cartridges use either one but that's a whole nother story.