I encountered something this evening that made me sit back and scratch my head.
While loading a batch of .309JDJ loads to take to the range tomorrow, I ran out of my first box of 150gr Nosler BT's, and opened another. Upon seating the first two, the overall length was 0.010" longer. A couple more, the same thing. Surely my micrometer seater die couldn't have moved.
So, I pulled one bullet from the original lot, and compared with the new box. Sure enough, ~0.010 longer in the new box, consistently. Is this to be expected? So, I adjusted the seating depth, and continued.
I am very picky about my loads -- make all my brass the same length, and measure every powder drop and OAL after seating. With this particular load, I am within 0.005 of the lands - where this barrel has it's sweet spot for this load. If I had not noticed the difference in OAL, I would have been into the lands and a possible dangerous pressure situation with near-max loads.
Anybody experience this? I now have a new section in my log book especially for bullet length. I will post any range results tomorrow.
Thx,
-Cm