drknite - I'm like you, I have a 40XB that is new to me and I'm trying to find information. The barrel tension screws on my rifle are backed out so as not to touch. The barrel is free floated back to about 1" from the receiver. It groups the best, with several different brands of ammo, and the receiver screws snugged up. I've tried it with the forward receiver screw slightly loose. This too, produces some very fine groups. I am surprised that no one person has replied to your post. I know that is disappointing when your seeking some help.
Don't know if this info is any help to you. Hope so! If you haven't already, you might check "Rimfire Central" and scroll down to the Remington site, then over to the model 37/40 heading.
Hope this helps,
27-T
