I know that it is standard practice to have dedicated fore ends on each individual barrel. That will be the ultimate goal, but I think I have found a pretty effective temporary solution. My fore end was vary close to fitting the same on both barrels, but had a little slack on the 444 barrel I just got after fitting it to the receiver. Figured if you could shim the underlug, why not shim the for end stud? After trying a few things I figured out that it fit perfectly with a small strip of pop-can aluminum inserted on the inside half of the mounting hole. This would be the near side if you were holding the gun to your shoulder. I cut a smaller section out of the strip and fixed it the the surface of the stud with standard super-glue. It should not be hard to remove with a little heat if I ever need to, but the fore end fits the same on both of my barrels so I might just leave it as is. I know lots have used shims on the fore end spacer, but this way, my fore end is just as interchangeable as my receiver