Stan,
I would make sure my scope base and mounts are tight first, like Bob suggested.
I assume you handload, so the next thing I did is vary my bullet seating depths. I usually start about .050" from the lads and move my bullets deeper in .005" increments, making 3 rounds at each new depth.
Before going to the range, I also use wide, clear tape (the kind used for taping boxes closed) on my hinge pins. This was to make sure my hinge pin didn't rotate while I was shooting it.
I went to the range and fired my 3 shot groups, looking for the tightest one(s).
I then made up 10 rounds of the most promising loads and returned to the range to confirm my previous test results, making sure I let the barrel stay fairly cool during firing 2-5 shot groups. I found 2 seating depths that were the tightest, so I went with the longer of the 2. Both groups were exactly .54", CTC, for 5 shots at 100 yards.
I used IMR 4064 powder, Nosler cases, CCI BR-2 primers, and Nosler AccuBond bullets for my testing.
Good luck and keep trying,
NightKnight