azrocks
Member
- Joined
- Jun 28, 2016
- Messages
- 659
I'm pretty new to hand-loading bottleneck rifle cartridges, in this case, 300AAC. What I have done so far has worked great, but that was with bullets with a cannelure (& some measure of crimp). I'm now working w/ 135g bullets w/o a cannelure, and have a problem.
I assembled a few dummy rounds (no primer/powder) with various levels of crimp, using a Lee FCD. The bullets are seated so that the entire neck of the cartridge is in contact with the bullet for maximum friction / holding power. Brass is brand new, trimmed just a few thousandths below the trim-to spec, & re-sized for consistency. I am belling the case mouth a tiny bit - without doing so these flat-base bullets simply fall right off no matter how well you try to balance them - but I emphasize tiny... just a hair. Crimp runs from just enough to take the bell out to as far as the Lee will go.
Thing is - no matter what - when I chamber a round aggressively by hand (AR platform) - the bullet walks a little bit out towards the lands. The more crimp the less pronounced, but even at full crimp they're walking anywhere from .002" to .005" each time the round is chambered, increasing the COAL each time. Zero setback, which I find surprising, as the bullets have an aggressive HP design. No matter how hard you slam them into the feed ramp, they don't set back. But they do come forward, each & every time.
These will be used exclusively in semi-autos. Where should I go from here?
I assembled a few dummy rounds (no primer/powder) with various levels of crimp, using a Lee FCD. The bullets are seated so that the entire neck of the cartridge is in contact with the bullet for maximum friction / holding power. Brass is brand new, trimmed just a few thousandths below the trim-to spec, & re-sized for consistency. I am belling the case mouth a tiny bit - without doing so these flat-base bullets simply fall right off no matter how well you try to balance them - but I emphasize tiny... just a hair. Crimp runs from just enough to take the bell out to as far as the Lee will go.
Thing is - no matter what - when I chamber a round aggressively by hand (AR platform) - the bullet walks a little bit out towards the lands. The more crimp the less pronounced, but even at full crimp they're walking anywhere from .002" to .005" each time the round is chambered, increasing the COAL each time. Zero setback, which I find surprising, as the bullets have an aggressive HP design. No matter how hard you slam them into the feed ramp, they don't set back. But they do come forward, each & every time.
These will be used exclusively in semi-autos. Where should I go from here?