I've been at this a long time and if you can't get Sierra MK's or IMR4895 to shoot in a 308 there is a problem some where between the trigger and the end of the barrel. Now granted there may be better combos. out there but these should shoot from just about anything there is out there.
Now if this was a hunting barrel you would not of read a single thing about this, because 1" is fine for hunting, but and this is a big BUT it was bought for competition and anything over 0.3 just doesn't cut it.
On a side note I just installed a factory barrel on a friends rifle and shooting the 150's it is shooting between .3-.4 , so a semi custom lapped barrel should do at least as good.