One problem I found that's unique to the 788 is that the rear action screw threads can bottom out on the receiver, and not hold the rear of the action properly. The threads on the rear action screw may not be threaded far enough to achieve proper clamping before the screw threads stop in the rear screw boss on the receiver. One fix is the thread the rear action screw further up on its body. Another choice might be to put a spacer (washer) between the rear screw hole in the bottom metal and the stock.My rifle had this condition. I added the washer and it helped a lot.
The other thing I did was recut the muzzle crown. There was visible damage to the original crown. A brass 1/4-20 round head screw and lapping compound in an electric drill worked for me.
My 788 tends to copper foul, so it shoots best loaded with CFE223 and a 165 gr partition.
I have a .308 M788 that was driving me crazy until did these fixes.
This may be an easy check. Loosen or remove the front action screw and check for movement.
