Apex Afterburner w/ strange results?

[Hudsflywater]

I picked up some 187 gn Afterburners to try out in my 300 WSM. I was a little hesitant due to the fact that when I chambered this barrel, I had a custom reamer made with an extra .200 freebore. The Apex ogive line is quite a ways back on the bullet, and long story short, even in a Medium length action, to get them to fit mag length they were jumping .140-.160". The only powder where I wasn't trying to load over 100% fill capacity was Sta-Ball 6.5. So I ran a. pressure test (10) shots, found pressure around 70 grains. At 68 grains it looked like good "positive compensation", and was at 2997 fps, right where I wanted it. So I loaded up 10 rounds to check accuracy. When I went to shoot them, they over 3000 fps, and showing signs of pressure? I only shot (5) and got home and pulled the bullets to make sure I hadn't f'ed up and put the wrong powder charge in, I hadn't. So how does a round magically go from 2997 to 3100 in two days using the exact same components? My scale is a FX120i and I trust its accuracy...

 

[wind gypsy]

No idea here. Was going to ask about barrel fouling differences between trips but that doesn't seem like a real possibility/cause.

 

[Hudsflywater]

Thats actually a good question, the rifle was cleaned before each test.

 

[PLhunter]

I know this is old but is the gun suppressed? Also, I’ve had this issue with Staball. Inconsistent pressure signs with the same load. However, I’ve also had some inconsistent pressure signs that I believe are tied to “condensation” from particulate in the chamber from using a suppressor.