Only the short magnum and target actions are a large shank, not sure about the ultra Mags, but it makes sense. The regular magnums are the same as all of the other center fire rifles (small shank). I have been thinking about doing a 10T in 300 Mag barrel swap with a 7x57 heavy sporter barrel because it is a cheap accustocked rifle and I don't mind the extra gap around the barrel from the 7/8 stock to the heavy sporter.