While many people suggest the seasoning of a barrel. Your barrel is stainless steel and might be a little hard to season with bore butter. IMO.. I would not suggest you do this. Your rifle is a modern rifle designed with some excellent materials. Now I will season my Grandmothers cast iron fry pan, but not my rifle barrels. I want that barrel nice and clean. A much better place for the bore butter is on a patch shooting a patched ball, or smeared on a conical bullet when you shoot that. Trash cans are also another good option. Again this is my opinion of the stuff. Other people use bore butter all the time with excellent results and by no means do I try and insinuate their way is inferior to mine. I clean my barrel spotless and then apply a good gun oil which I know will protect it from rust.

Two pellets and a 240 grain XTP will give you 1805 fps. This should be a lethal load to 150 yards if you can place it in the right spot. With the kind of accuracy you are getting, I think you are going to be able to do that.

If when you're loading it is one of these, lean on the ramrod and grunt to get that sabot down the bore, you might want to try Harvester Crushed Rib sabots, or the HP-24 MMP. I like the Harvester, they seem to work real good.

By the way, that is a beautiful looking rifle. I am sure that is going to be a great shooter for you....