I don't know how big your bears are over in Maine, but condsider the 300WM, which I have taken 4 of my 5 bears with. They don't make it too far after being hit with one of those, and after skinning him out it makes no difference. Tracking a wounded bear is fun if you end up finding him, but many are lost. That said you may have excellent shot placement and the .243 could drop him on the spot. If your paying big $$ for the hunt I'd err on the side of bigger caliber..my 2 cents