Brux, the 3 grain difference in case weight is nearly nothing. After I have fired my Lapua cases about 5 times, the weight will often vary about 3 grains from the lightest to the heaviest, perhaps about 171 grains to 174 grains. You may need to up your charge weight by a tenth of a grain of powder, but likely your load will remain the same. Ammo temp and/or ambient temp may play a small role.