Loved your observations on the 500. That a neat trick with the thumb on the safety,haven't tried that one. I shoot a Greifelt 500 NE and it is a thumper. I use IMR 3031 in it at 78 grs with a 570 gr bullet. Recoil is less than with IMR 4831. Also shoot a 450 gr LBT cast bullet with about the same load and its very pleasent to shoot. Regulates perfect. One other tip is to use 5.5 inch shoot and see targets when shooting a double at 50 yds. I find that me sight just covers the bull. Makes me shoot better.
I have a Merkel in 9.3X74R that I like a lot also.

Good Shooting.

Sam