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243winxb · January 22, 2013, 01:13 PM

Start with the bullets base at neck/shoulder junction. This is the full diameter of the base, not the boatail. Take a COL measurement. Load 5. Move the COL out/longer .010" & .020" Load 5 each. Then load some with a shorter COL. In .010" & .020" Load 5 of each COL for a total of 25 rounds. Test fire. COL must fit the magazine & not jam into the rifling. Most single stage presses will give a variation of about .005" COL with the same seating die setting. A progressive as much as .010" variation, same setting.

January 22, 2013, 01:13 PM	#17
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Finding the COL Start with the bullets base at neck/shoulder junction. This is the full diameter of the base, not the boatail. Take a COL measurement. Load 5. Move the COL out/longer .010" & .020" Load 5 each. Then load some with a shorter COL. In .010" & .020" Load 5 of each COL for a total of 25 rounds. Test fire. COL must fit the magazine & not jam into the rifling. Most single stage presses will give a variation of about .005" COL with the same seating die setting. A progressive as much as .010" variation, same setting.