I am assuming your ".300 WM" is a Win Mag., and not a Weatherby? Could be either, you know.....

IMO, as close as 40 yards it might cost you a lot of meat, using ANY .300 Mag.

Once had a .308 Norma, which is about the same(180-grain bullet @ 3150 FPS). Only thing I ever shot with mine was a caribou. My boss got a nice black bear with it, however....

When the RugerNo. 1 first hit the market, I just had to have one! So I ordered one in 7X57mm, OR .280 Rem., OR 7mm Rem. Mag. That was the order of preference. Well, don't you know that the only "7mm" available was the 7 Mag. It did the same thing to deer your 300 WM did (140-grain bullet @ 3350 FPS)-lost a lot of meat!! So I stopped using it for deer hunting, andgot a 7X57mm as soon as I could find one. Took me seversl years to get one, too!