Originally Posted by robocop10mm
H-110 is a very good choice for Magnum revolver rounds. I use a similar powder (W-296) for my hot loads in .357, .41 and .44 mag. Gray residue is well burnt powder. In the cast bullet loads, are you using H-110?
I would be a bit concerned of an overcharge. My experience with .41 mag tells me it is an efficient cartridge capable of exceeding .44 mag ballistics. The guns are marginally stronger than comparable .44's because of the smaller holes bored into the same size cylinder/barrel giving more steel to protect you.
I would pull a few of the bullets and weigh the charge. Triple check the charge weight against your loading data and the Hodgdon web site to make sure you have not goofed.
According to the Hodgdon web site the max load for a 210 gr JHP is 22 grains for 1631 fps (that is FAST!) and 26.5 gr for a 170 gr JHC yielding 1887 fps (that is REALLY fast!!!). I use 22 gr of W-296 with the 170 gr in all three of my .41 Mags.
It's possible that the "blowback" is unburned powder, I would be real concerned with overcharges of H-110 and probably 296 as well considering they are very much alike. Many years ago I knew a guy that thought it was cool to hot load .357 mags for his Colt Trooper with H-110, I looked at the top strap just above the barrel gap and the hot loads had gas cut quite deeply into the metal of the backstrap and had also eroded some of the barrel and cylinder faces. Basically the Trooper was becoming a piece of junk. I have used H-110 long ago, it's good powder but I like 296 as it seems to burn a bit cleaner in my 44 Redhawk, the shells have a light gray inside just like the inside of an exhaust pipe of a very good running car. When I loaded H-110 for my .357 Security Six that had a 6" barrel it would produce a ball of bright fire the size of a basketball at the muzzle.