[Unclenick]

In a revolver, as long as the bullet is still in the case and is not sticking out of the cylinder, it will usually function. If you seat it too short, though, pressure goes up. If you are developing your own load data, for Hornady swaged bullets or others that have no crimp groove, I usually just seat them so the front end of the bearing surface (the cylindrical full diameter portion of the bullet) protrudes about .020" to 0.50 from the case mouth. You can also simply call the bullet manufacturer and ask what they intended the COL to be for their load data.

If you want to use data from other bullets in a revolver, then you want to match seating depth of the base of the bullet into the case mouth rather than COL for that data. This is to keep the amount of space for powder the same, as that matters most to getting the pressure to match. It also assumes your bullet is the same weight and construction (lead, jacketed, etc.) as the original bullet used in the data. You need to know the length of the bullet and the COL in the data you are trying to adapt to your bullet. Subtract the length of your bullet from the original load's bullet length, then subtract the result from the original COL to get your COL. Keep in mind that if the first subtraction results in a negative number, that you add rather than subtract in the last step. Same rule as for subtracting negative numbers that you used in algebra class.

The above will work as long as the resulting COL doesn't stick out of the chambers in the cylinder.