I use a 50/50 mix of Simple Green and water in an ultrasonic cleaner for my guns. It will absolutely STERILIZE the gun--no carbon anymore, and it will also do a good job of loosening up the other fouling in the barrel.
Here's a caution, though--I also use an air compressor to blow all the parts dry, then I give them a good coating of WD-40, and let it sit for about an hour while I do other things. The WD-40 displaces any moisture left over.
I then wipe dry, and re-lube with a good medium weight oil.
Works great for me!
Hiding in plain sight...