The most powerful recoiling gun of any kind , rifles included , was a Freedom Arms model 83 with a 6 inch barrel in 454 Casull. I believe they were Buffallo Bore 300 grainers. In fact, I don't think they even load the 454 to those pressures any more ( this was about 20 years ago). I swear it was like a semi-controlled explosion in your hand. It didn't just hurt a little when you shot it. The dang screws on the gun would back out it was so bad. Contacted Freedom Arms about that and they said it was normal and to just tighten them back up.

If you are wanting to shoot full house loads for the Casull, then weight is your friend. That is a brutal round when you get it warmed up.