Help me interpret this Berger VLD COL test?

[Onewolf]

I made 30 rounds with what looks like will be my 'standard' 260 rem load: Lapua Brass, CCI BR-2 primer, 42.8gr Hodgdon H-4350, Sierra MatchKing 142 @ 2.840" COL.

I had remounted my scope, releveled the reticle and added a Vortex Scope Cant bubble level this week so I needed to rezero the scope. On my first target at 100yds I shot a cold bore shot, 3 scope zeroing shots, and then a 3 shot group to test the zero.

Based on the 3 shot group size, so far it looks like a good load.

Next I shot two 10 shot groups at 300 meters in order to verify 'consistency' of this load across more than a 100yd 3 shot group. The first 10 shot group was great, but the second 10 shot group wasn't nearly as good (mirage started kicking in and the bench started bouncing from other shooters).

It looks like this load will provide the accuracy I need as I continue to learn how to shoot long range (500-1000yd) field/match style.

 

[Bart B]

In an earlier post, you shot 12 shots and got hits with 11 of 'em. Good.

I suggest you test your loads with at least 12-shot groups; they'll tell you about 3 to 4 times as much credible information about their accuracy than 5-shot ones.

If you shoot two 5-shot groups with the same load and they're not within 10% of the same size, neither one's got enough shots in it to be 90% credible. If several groups with the same size are not within 10% of each other, they don't have enough shots in each one to be really representative of the load's accuracy.