Fantastic information. Thank you for sharing.
On a side note, I just completed load development with my 8 3/8" gun using 300 grain XTP MAG bullets and 4227 powder. Velocity is 1525 with an extreme spread of 14 fps.
My son will be using that load for a cow elk hunt in October.
I'm in the market for a 500 S&W. I already have the 460 XVR and love it, but I'm looking to add to the collection. The models I'm currently looking at are the two 8 3/8" models - SKU 163500 (muzzle break porting only on top); the 163501 (Hi-Viz sights and muzzle break porting on top and...
I believe the first two photos show the same marks you've described. The last photo shows the results after using a rust and lead remover shammy from MidwayUSA. Took all of 3 minutes to clean the entire cylinder.
In the past I tried CLP with no success in cleaning off the powder burns.