I would much rather see him get a brake installed, it will be VASTLY superior to any porting at reducing recoil. If you port a barrel properly, you have to inside ream the bore precisely and then port the barrel. In effect you will loose 1" to 1.5" of barrel length. Plus you will not be effective at reducing recoil.
Even if you take off 1.5" of barrel length and fit a quality partition style brake, you will get the same performance with MUCH better recoil control.
In reality the velocity drop from loosing 1.5" of barrel length in a rifle chambered for a 338 WM, would be meaningless, I would say less then 25 to 30 fps drop in velocity, totally meaningless and you would get much better recoil control with a quality brake.
Just my opinion. I correct dozens of rifles a year that have been ported and do not do much to control recoil, After fitting a quality brake, the owners are DRAMATICALLY happier with their rifles. They just wish they had done the brake first.
Kirby Allen(50)