Ralph is on the scent...
Check the travel distance of the FP. Compare the two .500's. If they are both the same distance, I'd assume the spring needs to be addressed. Things happen to new purchases...that's why the warranty. Call S&W and send it back to them. You might use the opportunity to ask them to smooth the action on it at the same time.
Sounds like you like the .500 Mag punishment and can afford the ammo. I would at least make it smoother.
I enjoy my .500 Mag too. I reload full house loads. I can't see the purpose to have a "horses leg" of a gun like a .500, just to spit out a soft load. There're much cheaper options out there.
It's the overall experience. The ball of fire, the dirt rising off the ground, the shear amazement that you've survived the concussion and the smile on everyone's face.
Just be sure to keep your grip behind the cylinder gap as you would on every revolver. This .500 will remind you why it's a good idea to keep your pinky's back.
I'm 6'8" and 270. I have big hands and shoot mine DA inside a 8" plate@ 7 yds. rapid fire with full house loads. Never more than a box after I switch hands. And never at the beginning of the range shoot. It will screw you up for the rest of the day.
My hands on my carry... You can see why my support hand could get in the way. Believe me, I've learned a long time ago.
It's fun to reach out 100 plus yards too. But you get tired quickly. It has a punishing recoil for sure.