9.3X57,
I am curious as to what your gun weighs, this 350 is not a lightweight. In the 60's, Remington came out with their model 660 which had an 18 inch barrel and was too light for the caliber. I shot one of those guns back then, and it kicked like a mule, but it was a couple pounds or so lighter than this gun, the 673. The 660 didn't last but maybe two or three years, then Remington discontinued it. Later on , they made up a similar gun that had a 20 inch barrel but it was too light for the caliber, also. It didn't last very long either. Over the years, they tried putting the 350 into various forms such as their classic model 700 and a couple of others, but none sold well, and I think alot of it had to do with their earlier failures.

I can only speak about my own experiences, so I will limit my remarks to those things I know to be true. The 660 I shot years ago put a really bad scope cut on it's owner after I fired it and gave up. He didn't have his scope set out far enough. That was not the fault of the gun, but was a fairly comman mistake made by the people you mentioned that were only used to shooting small bores.
It is a proven scientific fact that noise during firing is also perceived as recoil and if the earlier users were not wearing any hearing protection, (and most of us didn't back then), it may be that part of the perceived recoil was in fact, noise. These days most all of us use muffs or at least earplugs and both of those help when firing over a bench or offhand at targets. I know I don't notice the noise or the recoil when shooting at a game animal, your body just shuts it off, somehow.

My gun weighs just under 8 pounds with the scope mounted and I think that is about average for todays short belted magnums, so it is neither a lightweight or a heavyweight for the caliber. It may be that the shorter, stubby case make it more efficient and heavier recoiling than a longer, narrower case would. I don't really know. I have never been what I would call recoil sensitive in the past. I have shot plenty of hard kicking high powers and muzzleloaders with steel or brass buttplates, loaded heavily, and never had a problem. Then last deer season, I fell three times while hunting on ice over snow. Ya, I know, not the smartest move I ever made. In order to protect my newly made double 45-70, I took all the shock of the fall with my right shoulder, three times, before I could get out of there. In the process, I dislocated my shoulder and wrecked my rotor cuff, or so my doctor tells me. This shoulder will now slip in and out without the least bit of help. It will do it even by sleeping on it wrong. So I needed recoil protection in the worst way for the first time in my life. The Kick-Eze magnum pad gave me that and i will continue to use it and talk it up wherever anyone as an interest in reducing the recoil of their shotguns or rifles.
They work well and are a bargain at twice the price! Bob H.