Load testing 58gr vmax

[connnab]

So I've been doing some load testing for my Ruger gen 2 .243. 20" barrel, 1:9" twist. Last week I tested 5 different loads shooting 58gr vmax bullet over Varget. I found 44.1gr varget shot the best and gave me the best numbers. So I loaded up 6 more rounds of the same charge, exact same everything, and shot two more 3 shot groups yesterday. The speeds dropped almost 100fps for a few shots. No idea what I did wrong. Powder charge was right, I double checked every charge weight on a separate scale. I may just load up some more rounds of the exact same thing and shoot a few more groups to get a better idea, not sure.

Here's two groups, and their speeds shot yesterday.

Here is the same charge weight that's circled, 3 shot group shot last week. Numbers a lot better, I know it was only 3 shots. But no idea what the issue was.

 

[Seabeeken]

Has the brass been annealed? Weather change? I'd try a different powder with that light of a bullet, perhaps a bit faster burning. Just my initial thoughts.
My 8 twist 6AI doesnt care for light bullets but shoots .027 with 108 Berger EH

 

[connnab]

Has the brass been annealed? Weather change? I'd try a different powder with that light of a bullet, perhaps a bit faster burning. Just my initial thoughts.
My 8 twist 6AI doesnt care for light bullets but shoots .027 with 108 Berger EH

Brass has been annealed yup. Weather was about the same. Only thing I can think of is possible humidity change in my basement while reloading? Who knows. I used the same bullets and varget in my other .243 and they've always shot well. I'm gonna load up some more inthink and try a few more groups and see if it straightens out or if it's just not gonna work