I gave M-Pro 7 a tough test. I went camping over the weekend and brought two guns with me. The first was my Euroarms Rogers & Spencer black powder percussion revolver. The second was my 1945-vintage M-1944 Mosin-Nagant carbine, shooting some early 1960s-vintage Soviet surplus 7.62x54R light ball ammo.
We shot the R&S with 30 grains of Swiss 3Fg black powder. Swiss powder burns cleaner than Goex, but it's still black powder and leaves behind plenty of fouling. We put about 36 to 40 shots through the gun. Afterwards, no more than 6 patches wet with M-Pro 7 got the bore clean. It was similarly effective on the rest of the gun.
The Soviet surplus ammo we fired through the Mosin-Nagant is some of the dirtiest "smokeless" ammo I've shot, and of course it has corrosive primers. I also put a 5 round clip of Hungarian light ball through the gun. Again, only a few patches wet with M-Pro 7 through the bore got it clean. I followed up with a patch wet with Ballistol to verify that M-Pro 7 hadn't left anything behind, and it too came out clean.
We did our shooting on Saturday, I cleaned the guns immediately thereafter, and then I checked them the following Monday. Neither gun showed any signs of corrosion. I ran a patch wet with Remoil through the Mosin's bore and it came out green, indicating that the residual M-Pro7 and Ballistol left in the bore had been attacking copper fouling.
I am impressed with M-Pro 7. It is odorless with no fumes, not flammable, doesn't require any special ventilation, and according to the MSDS doesn't contain anything especially nasty. After years of using smelly, carcinogenic gun cleaners I think I found my new favorite.