@Jack Stevens
Loading nice bullets like the accubonds and 250 grainers or even the Barnes into the 350 REM mag greatly reduces the case capacity due to the short 2.8" coal.
The long 250grn Noslers can be an issue, but not so with the Speers or Hornadys, nor the Hawks. Haven't tried the Barnes 250grns.
If you didn't know, Remmy's initial factory .350RM ammo starting in the mid-1960s was the 200grn (@ 2710fps) and 250grn (@ 2450fps) loads, as chrono-ed from the M600 18.5" tube. Those loads went on to establish the cartridge's reputation on everything from mid-west deer to elk, caribou, moose, and the bears - black, brown, & grizzly.
The 250grn ammo was also used to take a cape buffalo in Africa, at least before the .375H&H became the legal minimum in most countries for DG.
Where loading the .350RM gets dicey, at least with the short-action platforms (to include the M600s, M660s, Model 7s, and an M7-derivatives like the M673), is with bullets above 250grns.
But where that line gets drawn on bullet size & weight isn't clear. I'm still experimenting with Hawk's 275grn and 300grn RTs, Woodleigh's brand being vaporware in my part of the U.S.
I've developed one somewhat accurate 300grn load with Varget. I was trying to duplicate the 300grn load that no less a reloading authority than Ken Waters developed using the Barnes Original 300grn bullet, getting 2200fps or so from his 22" Ruger M77. He recommended that load for big heavy DG critters.
If it was made on a standard action ( I know this defeats the purpose) and throated so the longer bullets can be seated out to utilise the case capacity it would be a different beast.
That's been done - long-loading - on the Rem 700, Ruger 77, and one custom .350RM Win M70 build I saw. The Remmy had a 24" barrel, while the Ruger and the Winny had 22" barrels. Those rifles all weigh about 9.5lbs or so with scope, mount, rings, and sling (i.e., field ready).
My scoped M600 is barely an 8b rifle all day, including the sling and stock pack. My scoped M660, with an 1.5" longer barrel and set up the same way, is just touching 8.4lbs.