Another option would be to chamber the barrel for 308 Norma. That is one of the things done when it was first brought out. You could get factory ammo and no gun.
Mag box should work, Follower might even work. It's only when you go to the Ultra mags that the box and follower have to be changed out. Open the boltface or swap out the bolt with a magnum bolt and you should be good to go.
Some is Good---More is Better----Too Much is Just Right
Does anyone still produce bolt action rifles in 300H&H?
They may be available special order in a new rifle. But, I cannot recall seeing any offered on an "in stock" basis in a long time. Occasionally, I'll see a Rem 700 Classic in 300 H&H like the one below come up on GB. But, the 700 Classics are only offered for one year in each chambering. Maybe 1983 for the Rem 700 .300H&H ?
Another option would be to chamber the barrel for 308 Norma. That is one of the things done when it was first brought out. You could get factory ammo and no gun.
30-338 is another good option and will give you plenty of mag box room to seat your bullets farther out.Cases made by necking down 338 Win Mag cases to 30 cal.Case is just a tad longer than a 30-06 case,2.494 for 30-06,2.500 for the 338.Performance about the same as 300 H&H.
~Molɔ̀ːn Labé Skýla~ As Bob Hagel would say"You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong."Good words of wisdom...............