Oaktree, what you have done by hitting the barrel cap is to actually twist the barrels in relation to each other. By hitting it you have rotated the barrel cap on one of the barrels until they were regulated. This is not the recommended way to do it. You should have loosed the clamp by undoing the torx screw on the barrel cap. These relaxes the barrel cap clamp on the left barrel. The trick is then to follow my instructions before then retighten the torx screw which will inturn tighten the clamp on the left barrel and keep the barrels twisted relative to each other according to the regulation required.

I do not under any circumstances recommend belting the cap with a hammer, if you managed to move the cap you have move the cap whilst it has clamped, if it doesn't twist back because you've loosened it, you may have removed your blueing on the barrel as you have rotated the clamp without loosening.

If you have a half decent scope and a bit of time you should be able to regulate to 200m which I would do for a 375H&H.