I picked up a couple of boxes of 300 WSM Custom Brass the other day. When working up my initial COAL, I tried an unprimed round just to see how it would feed. The bolt would not close all the way. This is on a Tikka T3. I pulled the projectile off and tried again, still no luck. I used a Hornady Lock-N-Load® Headspace Comparator and measured the length from the cartridge face to the datum line and it was about 1.747 - 1.746 on about all 10 cases that I measured. SAAMI has it at 1.7260+.0005, and my Modern Reloading 2nd Ed. Richard Lee manual has it at 1.730. I shoulder bumped a case down to 1.7415 and then the bolt closed, but still tight. Did I get a bad batch, or what is the datum line from the factory supposed to be? Anyone have a factory round or brass that they could measure to compare?