If you have uneven pressure from the stock on the barrel, the gun tends to shoot erratic, and the more you shoot it the barrel warms up and creates even more pressure on the stock. It will continue to shoot worse the warmer it gets, usually. Free-floating may cure it. I generally like about 1 1/2 to 2" of the barrel solid bedded, and the rest free-floated.
Another thing that comes to mind is the question of do you know if the lot numbers of your factory ammo have changed from when it used to shoot OK? If you have an old box from the "good" ammo around maybe holding empties, you may want to check the lot nos. with the new stuff that is giving you trouble. I've had guns turn from great shooters to barely adequate just with lot no. changes. Not terribly erratic, just not what it used to be. Handloading usually remidies this when the right combo is found for the gun.
You say you clean your guns faithfully, but unless you are using a good copper solvent like Sweet's regularly, you could have a copper build-up problem that will definitely affect accuracy.
As was mentioned before, keep your guard screws tight also.
Just a few things to think about...............