There's all sorts of possible issues if the stock isn't bedded for THAT action, so I'd think hard about at least trying a "skim" bed, making sure the old bedding is ready for adhesion of any new bedding.
The first and easiest way to get a clue is to either cut up some credit card or business card shims to temporarily float both the action and barrel. Just make sure the recoil lug is in contact with the shoulder as you tighten it down. But I've done that numerous times to get a clue and it can be amazing, almost night and day.
The other think you'd want to do is check your contact with either inletting black (ick) or Prussian blue (also ick). But either will force you to "clean up" and prep the old bedding for the new skim or re-bed.
I had to do that a couple of times, what I did was apply the blacking, crank stuff down as per usual, and then shoot the rifle. Then I pulled the action and that revealed the extent of contact without any doubt.
And the mag box might be secretly ruining everything. I don't know enough about Rem B and CDL's to know how the mag box is made, but if it's separate from the bottom metal, you could probably pull it out and shoot naked single shot and see what happens. Also, the shim trick above should get the bottom metal away from any action contact/stress, too.
