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.