Measuring COL

I've noticed when I seat my bullets then measure, I get a different # each time almost. But all are close

You may notice up to .015 or so difference in Over All Length, this is normal (most will be closer than this, but you may get one here and there that's a little longer or shorter). It can vary....if the primer is fully seated, and a variance in the bullets themselves. Pick up new reloading bullets from the box and measure them.... they're not always the exact same length..... close enough though. Sierra Match Kings are great bullets, but due to the way they are made, the hollow point at the end isn't always the same, therefore you may have a slight variance in their length. It does not effect their performance.

Overall length is a good starting point and should work in most rifles , but I use it most to see if a round will fit into a magazine or not.

Using a comparator to measure from the Ogive will be more consistent, but you will still have some slight variances. Sinclair makes one that looks like a nut, and is inexpensive, will do 6 calibers and it's easy to use.
 
Many people use the terms interchangeably - cartridge overall length and overall length.

In my records I use OAL to refer to the distance between the head of the case and the tip of the bullet. However as bullet shapes change, this is only really useful for controlling you reloads once a load is determined and set up.

I use COL to refer to the distance between the head of the case and the ogive of the bullet. This measurement is meaningful regardless of the bullet selected as it relates directly to bullet "jump" to the lands.

I only use COL for rifle reloading, and AOL for pistol.

That's me. I may learn something on this question.
 
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