NOT ENOUGH BARREL...

I've owned and shot several .338 Win Mags over the years and learned something important about them. A .338-06 works better with a lot less expense.

The 338 WM needs a lot of barrel to get bullets up to higher velocities, but you really don't need those excessive, higher velocities with the caliber. If you want more knock-down than a .338-06 (that easily gets 250gr. Sierras to travel at 2550fps), you need a BIGGER GUN! (Not that I'm opposed to that idea, my .416 Taylors work superbly.)

A 21" barrel on a 338 will probably just give you headaches - literally, as the muzzle blast will be considerable.

Reggie