I would start by tearing it down completely,take it out of the stock,scope bases and rings, and reassemble 1 screw at a time. Loc Tite scope bases and make sure tang is floated with action screws torqued correctly. And yes,some ammo will work better in your gun than others.Every gun is different and will like some ammo better than others. That's why a lot of us reload,we can change every variable to find what works. Sometimes it's very frustrating,but can also be very rewarding.