No question different bullets will group differently, generally not that much though. Second, if you're not using Black Horn powder then I'd switch right away. Make sure the scope screws are firmly set and are not working their way loose during the shooting sessions. If you find loose screws then remove them and use a thread sealant not the red, blue color, or just clear finger nail polish will work. Best advise, sight in with what you plan to hunt with then all the questions are gone. Lastly, I would see, if legal in your state, switch the ignition to 209 primers and get rid of the #11 caps. Most conversions run 30-40.00 and are well worth the money. For #11 caps I liked CCI but it has been several years since I've shot them.