Recoil reducer? I've had a fair bit of trigger time with my brother's Ruger#1H Tropical in .458WM. It is a fairly light rifle for the caliber, ~9lbs, with a plain barrel. 510gr factory loads are fairly stiff, 350 gr SPs aren't bad. Definitely a fun gun to shoot. My brother has a Savage Safari .458WM on order. The skinny little runt likes his rifles big
This gun has a muzzle brake. I assume you are against porting because of the noise/blast?
I'd suggest a PAST recoil shield, if you haven't tried one. These work wonders. Other options are installing buffers in your stock. I have no first hand knowledge of these. Gotta have some mass to the gun to tame recoil if you don't port it.
For practise/range time with your rifle, I'd suggest reduced handloads. I handload for my brother, and have a slightly reduced 350 gr load which is darn near MOA at 100 yds. That, and it doesn't rearrange your fillings