I've been struggling in my 6.5-CM loads with pressure signs (heavy bolt, extractor swipe marks, etc.) in loads that absolutely should "not" be delivering them. I'm talking about velocities that are hundreds of fps slower (2400-ish) than factory ammo (2700-ish) ... that by the way ... shoots with no pressure signs whatsoever. I was at a match this weekend whining about this, and an experienced shooter (that won the match) told me to loosen my neck tension and see if that helped. I'd never thought about that, but it does make sense that if the bullet is too tight in the case mouth, it could build up internal pressure that causes pressure signs but doesn't translate into higher projectile velocity. I size necks with a bushing tie, and then expand prior to seating with a L.E.Wilson Mandrel Die ... but that die is specifically and only equipped with a generic 6.5 mandrel. Assuming it's money well-spent, I've ordered the 21st Century die and mandrel kit to give me the ability to precision size my case mouths (the kit has a range of mandrel sizes over and under the standard) ... and see if I can solve this problem.
Anybody here agree ... that excess neck tension can cause pressure signs with low velocities? Just curious what the heavy-hitters here think about that. And ... am I on the right track with the 21st Century mandrel kit? Thanks! This whole journey is about continuous improvement ... at least that's what I keep telling myself.
