Cheers for all the input guys.
I've had it a few times when I've taken a shot, knowing it to be spot on, and it be out by a couple mil which I wasn't expecting. Always wondered if this was due to the ammo.

I'll have a look at the local RFD, see what they have on offer. Heard good things about Lapua from guys at my club, may try and get myself some of that.

Going to keep a record of my shooting scores to see if there's any noticeable change. I have data from Eley Subs going back to about April last year