Is this copper fouling?

Sure looks like it to me. I make a habbit of running a patch with copper cleaner about every 3rd time I clean. Can't give a logical reason the pistols aren't seeing any fouling.

Yeah. I'd say that's copper fouling. If it were rust it would appear in the crevices of the rifling first and appear splotchy. Rust seems to creep kinda like a fungi.

Handguns do get copper fouling, it just takes longer to accumulate. It's less prevalent because most handgun cartridges just don't generate the pressure and velocity to smear copper. Also, there is some math involved in diameter and bearing surface. Hopefully someone a bit more versed can explain it better.

That does make sense to me, the pressures behind those bullets probably far surpass that of a pistol. I also wonder if the depth of the rifling has anything to do with it. Most of my pistols have very shallow rifling, while the long guns are fairly deep.

Actually, the way copper fouling builds up, generally, is that the copper at the rear of the projectile is subjected to such extreme pressure and temperature that it atomizes. Once the projectile exits, the gas cools, and the atomized copper is drawn (attracted) to the steel. It is less attracted to stainless steel than carbon steel. The extent of copper fouling is also related to the extent of "courseness" of the rifling/lands.

That explains too why rifles sustain more fouling than handguns, more pressure, more velocity. I clean the rifle when I see accuracy begin to drop, or when I am done shooting and ready to store the firearm.

When I purchase a new rifle, I look for one that had zero to minimal fouling right from the factory. Krieger has some great reading about fouling, breaking-in barrels, etc.

Geno

Yes, that looks like copper fouling.

If it isn't having any adverse effect on performance I, personally, wouldn't worry about it.

BSW

Copper fouling in a rifle occurs from intense heat and pressure creating plasma. The copper is deposited in the bore as the gas like plasma cools. Very little copper deposit is from jacket deposit. Get yourself a copper solvent and a bunch of patches. Some manufactures say one brush stroke per round fired. Run patches and solvent until they stop coming out blue.

Clean the rifle bore with some copper solvent and a few patches. Then finish with a well patch well soaked with the solvent. Lay the rifle down on its side for a couple days. Then clean again. You will most likely get gobs of green copper crud out but the bore will be very clean. I've used Hoppes for over 60 years and never had any problems with it. Takes it a little time to do its job but is bore friendly.