Blr243 wrote:I have been reading about trailboss powder and there is a mention sometimes about filling the case to 70 per cent capacity. So I filled a 303 case with powder to be about 10 mm short of the extreme top of case as I thought that’s where the base of my projectile would sit. And I thought of that as being max case capacity. Then as I started to think about those 13:5 grains of powder and how I need to calculate 70 per cent of it. Then I realised I’m probably doing this wrong. So when they talk about Case capacity, do they really mean filled all the way up to the top of the neck. And that’s how case capacity is measured ?
Normally case capacity is measured for the full case using water, for TB they mean to the base of the bullet.
But I've never worried about it, I start by filling to around the bottom of the neck and then work up and down from there. I find there's rarely any velocity increase above that level though anyway.