Group Spreads@Longer Range?

[griffin ordway]

Particulars:
-Weatherby Vandguard 308 Win
-165 gr. Accubond bullet
-40 gr. AR Comp.
-Lapua brass, 2x fired/resized
-CCI BR-2 primers
-Redding dies: knocking shoulder back .002, neck sizing w/bushing die
-Perfect range conditions....no wind, 70 degrees
-Chrono stats reasonably decent: 2690 fps, SD 13, max spread 25

I did load development to get this baby to shoot 5/8 MOA at 100 yds. consistently. Then took it out to 300 hundred to verify and WOW, it shot well over 2.5 MOA!
I've had this happen with Barnes TTSX's because of their extra length to weight, and gave up on them because I was never able to get good consistency past about 250 yards. Been using AB for all my hunting rifles, in many calibers, for years now, and have never had a problem like this with them. I have to chalk it up to something in the reloading process.....but I don't know where to start. Anyone have any suggestions or insight as to what the problem could be?

 

[Carlos88]

Did you check runout? All same ogive length? Benchrest set up?

 

[griffin ordway]

OK, I figured it out. If you all want to chuckle at a bonehead move on my behalf, here's what the problem was:
Decided to check the fired brass for pressure signs, anomalies, etc. While doing so I realized that 3 of the 5 cases were Federal brass...not Lapua!
Some factory brass somehow got mixed in with my reloading brass, and bonehead me didn't inspect the brass well enough to catch it. Makes sense now, because the group pattern is two nice tight holes in the center of the target, and 3 totally out there flyers. Lesson learned. Will load up another batch of "good brass" and re-shoot....willing to bet it shoots lights out.