They;re all hammers. Call SSK and get the scoop from Jones. The 375 bullets work in the JDJ! I have a 375JDJ in a 15" and used it to punch right a big 6x6 bull at 175yds. 3 times. My 285speer grand slam sneaks out at between 1975 and 2015fps. I choose it over my TC 30'06. It drops a little more, but out to-250yds, the animal is mine! I don't think anything can stop it. All of the Speer bullets work. The 235, 270 and 285's have all hammered PA deer, and of course the Elk. I think the Sierra 250 and 300 Boat-tails fly wonderful, but they need an H&H velocity for expansion to be dependable. IMHO, I think the 375 is the most versatile round there is. Is this a Contender or an Encore? I'm guessing the former. If it's Encore, Have you considered the 375-06JDJ? The write-ups seem fantastic! I don't use big-kickers in rifles anymore, I've had eye surgery and although my Dr told me to go ahead, I don't take the chance. I have relegated my recoil to being absorbed by my hand and arm. I love the big guns. I am really interested in the 338's and I am looking at the JDJ and a 338-08.
Good luck! Topgun.