Because elk is on the mix, from 100-800Y, and working towards at least 1200Y,
"my" choice is .33 cal - .338 RUM/Lapua/Norma Mag, etc. - a chambering that delivers enough velocity and energy with the right bullet to harvest an elk humanely. Shot placement and the NUT behind the trigger remain the most significant factors. If he stays under 800Y, there are more options.
Berger sells .338 LM with 250/300 EH, and 300 OTM, HSM sells 250/300 ORM for .338 RUM/LM for the 1200Y elk poke.
Berger's ammo loaded with 300 OTM shows an MV of 2725 FPS. At my altitude at 1200Y, it has a 1701 FPS and 1927 FT-LBS.
As far as gunsmith, contact
@Alex Wheeler.