So after reading as much here as I could, I loaded my first 450BM rounds. I am loading 275 gr. Barnes TSX over H110 to do some testing to see what my rifle likes. I have the 4 piece Hornady custom dies. I am shooting an AR15. I have loaded one other cartridge prior to this (6.8SPCII) but have no experience with crimping.
After seating they were all measured at 2.26" OAL - I then placed a taper crimp which measured .475 at the mouth/taper. At this OAL this has my crimp above the last groove on the bullet. After I finished, while moving them I dropped one which tumbled off my knee, hit a box and then landed on the floor. I rechecked the OAL and it was now 2.245". I am certain it was 2.260 before it fell. The bullet does not look altered in any way; as a double check it I grabbed a comparator and measured from closer to the ogive and it seemed to confirm the bullet is seated .015" deeper now.
I am not feeling so sure about my taper crimps at this point! Should I go back and put a little more crimp on these? Will the shorter round (OAL 2.45") still be safe to fire? I'd appreciate any thoughts on what I've done so far.