This may cause the action to bind, and that will quickly wreck accuracy. Get the action screws good and tight with hand tension, but do not dog them down with a torque wrench. Take a quick look at the barrel channel. Most factory rifles are free-floated in the barrel channel because this is the simplest and easiest bedding technique in a production rifle. Horizontal stringing of a group is almost always caused by uneven pressure on the barrel.
Some rifles are fairly tolerant in that they shoot fairly well with a wide variety of ammunition.
If everything checks out the simplest thing to play with is the loads. While accuracy gains are usually relatively small, this is one area where you might see dramatic improvement. Some rifles are fairly tolerant in that they shoot fairly well with a wide variety of ammunition. Others are very finicky and almost all will shoot their best with a few loads and absolutely terribly with a few other loads. Note that the good loads in one rifle might be horrible in another, and vice versa.