It was many years before I thought I could manage what might be considered a powerful rifle. In my early 20s I was hooked on the .350 Remington magnum, which I got in a M-700, as the supply of 600s and 660s in my area had pretty much dried up. I had a little pocket book that had a 2 page picture of a fellow with a 600 Remington .350 magnum, and a huge polar bear that he had taken with it, out on the sea ice; for some reason that picture grabbed my imagination. The old style 700s with the thin forends didn't stand up to the recoil of the fat little .350, and was soon split from the checkering in the forend back deep into the pistol grip. I intended to get it restocked, but the gunsmith I chose went bankrupt about a month later, and it took me over a year to get the rifle back from the receiver. Some of you older guys might remember Campbell's Gunsmithing in Winnipeg, there was even a write up on Mr. Campbell in Gun Digest; I don't recall why I decided on them when I already had a good relationship with the folks at Jennings back when they were on Garry. I traded the .350 off a short time later, with less than 100 rounds down the pipe. I don't recall shooting that rifle upsetting me; the 700 stock fit me pretty well when I was young and skinny, even if I didn't understand such things then, and the cartridge was only the power of a .35 Whelen.
Next came the first version of the M-95 Marlin in .45/70 with a 22" Microgroove barrel. My hot load with it was a 405 over 52 grs of 3031, lively but no .458. Later, I was exposed to 2 rifles that hurt me, both chambered for what are normally considered moderate cartridges; one was a 98 Mauser of dubious Latin American heritage that was chambered for the .30.06 and was still in military trim and wore the K98k stock. Wearing a T-shirt and firing Winchester factory 180 gr ammo, that thing bit! Later there was a Mosin Nagant carbine in 7.62X54R. What the Russians had against their own troops is a mystery, but if the idea was to keep them pissed off, shooting that rifle with it's steel crescent butt plate, would certainly help. It occurred to me about then that a 6.5X55 was the correct answer for me, except that the Swede didn't fit my lifestyle particularly well. I developed a tolerance for the .30/06 and it quickly became my sweet heart cartridge first in a Herter's stocked '03 Springfield, then later in a M-17 Enfield. I did a short stint with another with a Mauser in .458, but pretty much loaded it to .45/70 levels. A Pal of mine let me have a workout with his factory Brno 602 in .375 H&H, but the LOP was excessively long for me, as I had developed thicker shoulders and chest by then, so I needed a shorter LOP. As a result I ended up with a sharp pain, not in the pocket of my shoulder, but actually in my shoulder blade, and once again concluded, that a powerful rifle wasn't in my future.
I was a big Ross Seyfried fan at the time, and he got me interested in the .416 Rigby, his graphic description of what it would do to a lion convinced me that's what I wanted in a bear gun. It wasn't long before Ruger introduced their #1 in .416 Rigby, and I decided I had to have one. By this time I was pretty much satisfied with my M-17 Enfield in .30/06 for any shooting chore that came my way, including bear work, but that .416 quickly became the rifle I was seldom without. Not surprisingly the first butt stock cracked due to uneven bedding with the receiver. This was quickly replaced, and the replacement was shortened up to provide a 13.5" LOP including a Decelerator recoil pad. I got to where I could shoot 3 rounds with a 350 gr X Bullet or Speer MagTip over 102 grs of H-4350 from prone. The 4th round always pounded me for some reason, so I kept my shot strings short. I exchanged the factory quarter rib for a custom one which put the ocular of the 1.5-5X Leupold mounted in Tally QD rings even with the front of the falling block, thus keeping the loading port unobstructed, and reducing any chance of getting tagged by the scope regardless of my shooting position. Although a bit late, thus began my love affair with powerful rifles. That rifle was unfortunately lost in a house fire, and was replaced by a Whitworth .458, which I later traded for the Brno 602 that hurt me earlier. That Brno, became my full custom .375 Ultra carbine. But is was a .416 Rigby in a rifle that fit me, with its scope repositioned so as not to cause an injury, that hardened me to recoil, and allowed me to enjoy the benefits of these rifles.
The point of this diatribe is that I believe any normally fit and active adult can become comfortable shooting rifles in the .338, .375, or even in the .458 class. First though you must really want to master them, and secondly, you must be able to handload so that you can start at a tolerable level, then work up to the the cartridge's full potential. If you find that a 7 pound .30/06 upsets you, you have a ways to go. But like me, you can get there if you want to badly enough.