OP, unless the smith screwed up the crown and left dings or worse in it, or your action screws aren't properly torqued down, there's a pretty high likelihood changing the barrel length put its accuracy nodes in different places with the load you have been using, as mentioned above. Before going there though, check the crown, check the torque on the action screws, maybe give it a patch down the barrel to see if anything comes out, and also check to make sure the scope's mounting is all properly torqued, before you mess with your loads at all. It's a bit like when your car won't start - think common, easy things first before jumping to more unlikely but severe problems. Foot on brake, battery cables fastened properly, battery works, etc, before thinking it may be the computer or starter.
