One thing I didn't mention in the column is that after establishing an accurate seating depth for one bullet, it's relatively easy to seat another bullet so that the ogive is the same approximate distance from the lands.
As an example I'll use a .30 caliber bullet. After establishing a good seating depth with one bullet, the same approximate ogive-to-lands distance can be obtained by setting a standard steel caliper to .304", then using this setting to inscribe a circumferential line on the seated bullet in front of the case mouth.
The distance from the case mouth to this inscribed line can then be duplicated relatively easily on bullets with slightly differening ogives. Just inscribe a circumferential .304" line around the ogive of the second bullet, then seat this bullet so that the line is the same distance from the case mouth as the line on the original bullet.
In fact, this is the method I use when testing lots of different bullets in one cartridge. It is very easy to establish the same approximate ogive-to-lands distance with several different bullets using this method.
John, my friend is trying to get going on some Berger's in his .243. Where would you scribe the line? .240? I found some bore/groove numbers on Dan Lilja's website and that LOOKS right to me.
Anyone have a chart of various bore/groove diameters for different calibers?
Thank you sir!
If I scribe a .308 to .300 its a nice match to my Hornady comparator body...i'm not sure if it means anything other than it's a....nice match....and I can't eyeball that small anyway :P
