Let's start with the basics, what size groups is your rifle shooting, and what are your expectations? If you are shooting factory hunting ammo and are getting 1.5 minute groups, that might be all you are going to get. If on the other hand you can't keep the groups smaller than 3 minutes, you have a problem. Next time you are at the range, dry fire at the target. When the striker drops, is the reticle still centered on the target? If not, you might not have a rifle problem; your position needs to be adjusted or your technique needs work. Even when shooting from the bench, a light powerful rifle like yours needs to be held firmly in both hands, and not allowed to free recoil.
Check the scope, mounts, and screws as said above. If you don't have an inch-pound torque wrench think about getting one, many shooters over tighten scope ring screws which need only 20 inch-pounds with steel rings and 15 inch-pounds with aluminum. The windage screws can be tightened up to 30 inch-pounds, and the recommended torque for action screws can be as low as 40 inch-pounds for wood stocks without pillars to 60+ for synthetic stocks with pillars. A gunsmith once told me that torquing action screws to more than 50 inch-pounds has no benefit, and will cause the screws stretch. I don't always follow that advice, but I always remember it. Screws should have a drop of blue or green Loktite to ensure they stay put. A drop of nail polish that covers the edge of one scope ring where it meets the scope tube will allow you to see any movement of the scope in the rings.
Are you confident in the condition of your scope? It might not be tracking, or perhaps not holding zero. If possible, mount a scope from a rifle that shoots well, and see if the problem persists, or mount this scope on a rifle you know to be accurate, then see if it shoots. Leupold produces a good product, but if there is any question concerning the condition of your scope, send it to the Korth Group for a free inspection and adjustment, repair, or replacement.
Check the bedding between the stock and the action, look for evidence of movement. Is there a mark on the underside of the barrel from a pressure point in the forend's barrel channel? The height of the pressure point can be measured, then removed, and replaced and adjusted later if necessary. If the forend can twist in your hands when moderate force is applied, the rifle would benefit from stabilizing the forend. I believe that Nathan Foster's stock stabilizing kits will be available in Canada again soon, you can check his website at Terminal Ballistics Research. I used this stuff on a particularly flimsy plastic stock, also a .300 Winchester, and the difference had to be seen to be believed, it turned a stock with the rigidity of a wet noodle into one as rigid as any top quality fiberglass stock. Stock stabilizing should be done prior to stock bedding; most mass produced rifles benefit from a bedding job.
