Thread: My first load development

Originally Posted by Remmodel7

Yes realize one group is not definitive but I have to start somewhere. Plan on loading a few more, Checking velocity and looking for pressure signs at that load.
How do people calculate velocity change compared to book data from a 26" barrel in the load data to my 20” barrel?

Greetings Remmodel7,
I have not found ejector hole marks all that reliable as an indicator of pressure. There can be a slightly rough edge around the hole that makes a mark at normal velocities. Another rifle may show no mark, or any of the other "pressure signs" but expand the case head beyond further use with one shot. I've seen both. In the second case the claim was really good velocity with no pressure signs. Old data that had not been pressure tested was a culprit here as well. Velocity is easily the best indication of pressure that can be used by handloaders. Actual tests of velocity loss v barrel length reduction have shown 20 to 30 fps loss per inch for standard calibres with the smallest cases losing the least. I would figure on 20 fps per inch for your Grendel. Hodgdon/ADI book data for the Grendel is for a 24" barrel so 80 fps would be right.
Regards Grandpamac.