I noticed on quick-load that the case capacity of the 9.3 X 74R is ~84 grains of water, compared to ~88 grains of H20 for the 9.3 X 64.
This got me thinking: why not "hot-rod" the 9.3 X 74 to more modern pressures and get w/in ~100 fps of the 9.3 X 64? A 250 gr Nosler Accubond (or Barnes TSX) at ~2600 fps would make the 9.3 X 74 a legitimate 300 yard cartridge.

With modern quality brass (i.e. RWS or Norma), is there any reason potential problem with doing this in a Ruger No. 1? I can't think of one, but I thought I would doublecheck before I do something stupid...

Nope, just go ahead! Why not improove it while you are at it? Increased speed and lifetime for the cases!
Hotrodding original cases in original chamber would strech the cases rather fast.

Sounds like a good candidate for an Ackley Improved ... just a big 30-30 AI

I think you would be ok w/ RWS but the Norma brass is very thin in the head/web area. I have a #1 in .338x74Keith based on the 9.3x74R necked down & "improved". I run 250gr bullets @ 2700fps & the Norma brass only lasts 5 firings before head sep. starts to show up. The RWS brass I have been using lately is on 7 firings & still looks good. When I sectioned both cases, the RWS is almost 1.5x thicker in the head/web area.

You might like to talk to hornady about the brass they are are will soon be producing , for the 9.3X74R. The case is so taperd it would have a lot of streaching to do, but then there would alot of increased powder space too.
FYI the latest Nosler manual shows a load of 67 grains of Viht 550 with a velocity of 2653 pushing a 250 grain Balistic tip, and i think they have a 250 acubond now.
great load for elk or moose. Big bears too if you want to shoot one with a single shot...tj3006

Isn't it easier to just buy a .375 H&H?

analog - I'm with you on this topic.

I see a bunch of 9.3x74R's used here for Drive Hunts - the cartridge does a spectacular job just the way it is.

I don't have the rimmed version but a 9.3x62 - lovely rifle that's does what it was intented to perfectly with my hoarded supply of Nosler Ballistic Tips, when I want to bash something harder I use my .375H&H.