a 416 or 458 is WAY more than 45-50 ft lb in an 8-9 pound rifle! a 416 with heavy loads is closer to 80 in a 9 or 10 pounder. A 50 BMG at 30 pounds will be less, I’ll give you that one.
Umm, no, free recoil for a 416/400 at 2400 is 58 ftlbs in a 9 lbs rifle. How do I know? My Ruger No1 and a free recoil calc tells me so. Chiropractor in a cool package....
The Win 70 458/500 at 1975 ( never found a factory load that actually reached the advertised 2150 from it’s 24 inch bbl) is nearly the same, but less sharp. Both are easy to shoot, but certainly not like your 223.
Best
The Barret XM 107 (M82) with 30 in bbl at 24 lbs with optic is much less of an issue, but blast is the biggest uncomfortable aspect- the break works by moving gasses laterally and rearward.
The worst felt recoil I enjoyed was from my m’s P17 Enfield with feather weight bbl and very thin stock-6lb, left bruises like no other rifle- in 30/06; no wonder she didn’t shoot it much, 5-3/120lbs gal.