Firearm and ammunition manufacturer's are always coming out with new products and promoting them for sale to the public. This is how they stay in business. Most of the new Ultra magnums and short mags are just calibers that were already out there repackaged. Examples the 300,338, & 375 Rem. Ultra mags do nothing that the 300,340, & 378 Weatherby mags would not already do. This is of course if you are using Weatherby ammo. The short mags only duplicate the ballistics of the 300 Win mag and the 7mm Rem mag. They are just packaged in a short action. An action that is 1/2" shorter and an overall rifle length that is 1/2" shorter and only 4-5 oz. lighter doesn't make much difference to me. So, basically it's simply a marketing twist to sale new rifles and new ammo often at inflated prices at first. It's human nature to want something new and improved even if it's not really improved just new. I have many friends that have fallen for the trap of buying and ultra or short when they already have the same caliber in a different magnum. Such as, my neighbor. He has a Winchester model 70 300 Win. Mag w/24" barrel. This rifle with 180 loads I make for him will shoot 3/4" 3-shot groups on a regular basis. He bought a Win model 70 featherweight in 300 WSM. I again produced him a 180 gr handload that is very accurate. Although, he gets about 150 fps more velocity out of his 300 Win. Mag. So, what is the point. He wanted something new!