Don't know about most guys here, but for the very few amount of times I use a gun-scrubber product I have no problem spending the 8 or 10 bucks they charge for the Birchwood-Casey brand stuff that was actually meant for cleaning guns. At least I KNOW it was developed specifically for that usage.
I sure as heck make sure the gun is completely disassembled so no other material that they use on guns like rubber, wood, etc gets sprayed. Also since these type of cleaners remove all oils and rust preventatives from the metal, all areas must be exposed so that they can be re-coated with a lube and rust preventative.
Since I am not a Chemist or Chemical Engineer I have no way of knowing not only the exact ingredients that they put into these chemicals, but the proportions that they use. So unless you clean guns professionally, I would personally recommend a product made and sold for such purpose.
YMMV.