Both the 303 and 30-40 will kill anything in the lower 48 with a 220 grain cast bullet.
A Highwall or No. 1 is no fun to shoot in either will full house loads.
I question this. What gun are you shooting? Many hi walls offered for sale to day have the curved butt plate and straight grip or one of the two evil feature. That is not good. I have the BPCR version which has flat butt plate and grip design but also a heavy barrel. Kinda Apples to oranges. I also have a limited edition medium 28" round barrel '85 with pistol grip and shotgun style butt plate. Both are very easy shooters with max BP loads and 500 gr bullets. Looking at the Courtney, it really should be fine on recoil with in a great over all handling package. Good rubber butt plate and pistol grip. If I were buying one, it would be a 45/70. That is where the fun is for me. But, I already have two repro 85's, both in 45/70, that puts me in the same boat as Pappy. I handled a Courtney in the gun shop. I was impressed.
Maybe a 405 Win or more a British flavor might be a 450/400? Probably not in my budget in any caliber. Post Covid, my dollars just not covering life the way they used too. If I was still working the Miruko 1895 in 405 would be tempting with a companion in an 85. Not an option. Miruko is scheduled to do a '95 in 405 (again) this year (2022). The worthless paper dollar is killing me though.
Speaking of 450/400 I have that in a No1. It kicks but; nothing like a 458 that will really slap you around hard. That includes sitting on the bench, which is worse case. The muzzle rises you roll back a bit. Not the punishment one might expect. I know it is all subjective. The Courtney should be just fine with any load. My 8c adjusted for Covid.
