I have both a model 51 and a model 651 and like them for field carry on my property. I usually have them loaded with three rounds of Gold Dot magnum cartridges (groundhogs), two rounds of WRF cartridges (edible small game), and one round of magnum #12 shot(copperheads too close to actual house).
As much as the the 51 and 651 serve their duties well, a more recently purchased 631 (4 inch .32 mag kit gun) is now being carried more often with a similar combination of cartridges (magnum 32s, 32 longs, and handloaded shot shells). I find the .32s a little more pleasant to shoot (less muzzle bast) and a little more effective on game.
All three are great guns and will be among the last I will sell.