I am getting ready to start my build for a 257 Roberts on a Model 12 and am thinking of using a PacNor barrel because I can get it with a 1:9 twist for longer mono bullets and heavy leads. I notice on their website that they recommend a gunsmith fit the barrel to the action. Does Pacnor leave a step or two out that a gunsmith has to perform or are these barrels a true prefit/drop in barrel? This will be my first barrel swap but it seems pretty straight forward. Any advice would be appreciated. Thanks.