If the recoil of the 338 mag is too much, then lighten the load. Slowing the bullet down to Whelen velocities does not take away the SD and BC advantages, and it will still kill game.
If you're hunting deer or the like with your 338 mag, then use a lighter bullet to reduce recoil. It doesn't take a 250 grain bullet to kill deer, and you don't have to shoot max loads all the time. A decent 200 grain bullet at 2600-2700 fps from your 338 mag will flatten deer and be a pleasure to shoot.
I have a perfectly good deer load for my 45-70 that shoots 400 grain cast bullets at about 1000 fps. I can shoot them all day long. When I carry that gun elk hunting I change to 350 grain jacketed bullets at about 2100 fps with a case full of H322. It's a totally different rifle with that load, believe me.
