Most that use them for hunting shoot them a handful of times to sight them in and however many shots needed in hunting season.
Your not going to see anyone at the range testing 100's of 416 Rigby....
You've obviously never been out with my family.
The average day with the big boomers (every 6 to 9 weeks) sees each shooter absorbing recoil from 80-120 rounds, spread out over 2-5 heavy hitters:
.450-400 Nitro 3.25" - 20-30 rounds
.444 Marlin - 20-50 rounds (6.3 lb Handi-Rifle nicknamed "Thumper")
.416 Rigby - 25-40 rounds
.375 H&H - 40-60 rounds
.375 Ruger - 20-30 rounds (recently sold)
.338 Win Mag - 40-60 rounds (multiple rifles)
.300 Win Mag - 20-40 rounds
In the past, the average day with .458 Win Mag (multiple rifles) was well over 100 rounds - often 150 to 200.
(A sometimes not-so-smart owner bought a substantial quantity of a bullets that turned out to be horribly inaccurate in all of the available .458s; and decided to sell his own .458s. So, they were used for 'blasting' ammo.)
And, then you get into the mundane "light" stuff:
7.62x54R (multiple rifles, heavy loads - not the light ball surplus crap)
.30-06 (multiple rifles)
.270 Win (multiple rifles)
.45 Colt ("Ruger" loads - multiple revolvers)
.44 Mag ("Ruger" loads - multiple revolvers)
.357 Mag (multiple revolvers)
.327 Mag (multiple revolvers)
And, a new addition: TC Encore, currently wearing a 10" .30 WCF barrel.
All the smaller stuff (.243 Win, 9mm, .32 H&R, .22 LR, etc) feels like an air gun, once you play with the big boomers for a while.
It takes one round to decide it hurts.
It might take 3-5 more, to figure out what you're doing wrong, and to make it stop hurting. From there, you're just wearing yourself down with muzzle blast and recoil. When you're fatigued, it's time to quit. If it starts hurting again, you're doing something wrong.
We go (ground) squirrel and rabbit hunting with the big boomers and 'magnum' handguns, at least twice a year, as well. It's great practice, and you don't really feel recoil or much of the fatigue in a hunting situation.
Some people "bark" tree squirrels. We occasionally "mud" ground squirrels. There's nothing quite like firing a .416 Rigby into a mud bank one or two inches below a squirrel, and watching them fly through the air... stone dead.
There you were
sitting on a mud bank.
Launched into the goo.
It was hydraulic shock
That catapulted you...
(Sorry. Space Oddity
popped into my head.)