Quote Originally Posted by Airgator0470 View Post
Too many variables... you will have to go hands on with a practical application to get the answer IMO. I think it's best at estimating velocity... but I don't know, never used it, just hear people referring to it for start load data with different powders.

ADDED- it mentions bullet seating depth estimates are "crude", in other words... a rough guess.
I apologize. This is a topic twist but in my opinion a fascinating one, and that reminded me I wanted to point it out.

300 BLK
20.2gr H110
110gr Barns TTX (.30 caliber)

Called Barnes because the data I could find did not specifically mention that bullet, it was for the TAC-X. Barnes said to use the TAC-X data. Specifically including the COAL.

Tried that. didn't work ~at all~. The "top" of the boat tail was dead level with the top of the case. Nothing to get a crimp on, not enough full diameter bullet in the case to even try and kid myself it *might* not need a crimp.


So, I did a little measurin.

I was keenly aware that the powder charge was right at where the case neck starts at the top of the taper from the case body. I don't like compressed loads. It has been my experience that pressure goes UP exponentially and even a few flakes of powder can make a noticeable difference in pressure and thus velocity.

So I did a little measuring of exactly how much room there was between very carefully measured powder charges and the top of the case. I considered this my absolute rock bottom - bottom line for bullet seating depth.

I made three rounds seating at the top edge of the bottom driving band on the bullet.

I made three more rounds seating the bullets at the top edge of the middle driving band. Which by the way measured EXACTLY at my bottom line bullet seating depth.

I crimped all six rounds the same, and took off over to the range.


The longer coal cartridges had 250-300 FPS more velocity than the shorter coal cartridges.

As a side note; the longer COAL velocity put me dead nuts on the projected velocity; 2450 FPS. So given that I was so happy I kinda forgot about the shorter COAL actually losing velocity. Until Bob reminded me about coal being a 'rough guess'.

Strange stuff indeed . . . .