UPDATE:

Since getting all the advice, here are the steps I've taken:

1. Removed all copper from barrel and clean thoroughly using Wipe Out and Patch Out products.

2. Bought some Federal Gold Medal Sierra Match King ammo to test against the copper Barnes, Black Hills Gold and others I've been working with thus far.

3. Shot it; saw no improvements. The Match Kings showed the same pattern (one or two shots here, then one or two shots there about an inch and a half or more apart and in an unpredictable order).

4. Put it on the bench, removed scope and mounts. Found nothing obviously loose. Tested scope on a hand-mirror using the method described earlier in this thread (align the two reticals, whack it against my hand, check for misalignment, repeat). Found no movement. Did manage to confirm that Vortex scope knobs are possibly the least satisfying dial to click of all time, though.

5. Here is where it gets interesting. Loosened the action screws one by one and checked for movement in the gap between the tip of the foregrip and the stock. Found that while the front action screw produced no movement whatsoever, cranking down the rear action screw actually produced a slightly wider gap between those points. So I'm getting some clamping action that is putting torque on the stock.

The question now is what exactly went wrong during the bedding job, and how do I repair this? I realize that the most obvious step would be to grind out all of the existing epoxy and start over from scratch, but I'm curious as to whether or not it may actually be repairable short of an entire re-bed. Maybe I could add a small amount of epoxy on top of what's already there instead of grinding everything away entirely?

One thing I wonder about is that my bedding guide advised relieving the rear action screw by enlarging the hole slightly to ensure it doesn't push on that screw laterally at all, but perhaps since that is the opposite of pillar bedding, it's allowed the screw to apply too much clamping pressure on the wood of the stock?. Maybe adding pillars is the answer?

Any advice is welcome. What would you do?

Thanks,

Blake