My first one

ithacaartist · 07-20-2012, 06:56 PM

That number represents the measured dimension of the bbl. between the lands. They are usually in the range of 8.81, 8.82, 8.83. Since this I.D. is a little more than a tenth of a mm smaller than the 9mm slug, the lead or jacket gives way this much, causing the slug to ride the lands as it exits the bbl., establishing its spin. I think the middle number is actually a misstamped or deformed 8. Look more closely. On a refinished bbl. sometimes they have been worked down enough that the numbers start to disappear.

07-20-2012, 06:56 PM	#1
ithacaartist Twice a Lifer Lifetime Forum Patron Join Date: Mar 2011 Location: Atop the highest hill in Schuyler County NY Posts: 3,400 Thanks: 7,555 Thanked 2,643 Times in 1,393 Posts	That number represents the measured dimension of the bbl. between the lands. They are usually in the range of 8.81, 8.82, 8.83. Since this I.D. is a little more than a tenth of a mm smaller than the 9mm slug, the lead or jacket gives way this much, causing the slug to ride the lands as it exits the bbl., establishing its spin. I think the middle number is actually a misstamped or deformed 8. Look more closely. On a refinished bbl. sometimes they have been worked down enough that the numbers start to disappear.