M.A.P. which is a combination of Murphy's oil soap, isopropyl alcohol, and hydrogen peroxide does work well. I personally mix it 20% murphy's, and 40% each of the alcohol and peroxide.
It will cut the fowling and a lot of the other crud out of the barrel very well. The problem is any time you use hydrogen peroxide in your rifle it causes flash rust to form and it will surprise you how fast that stuff shows up.
Like the others said, clean the rifle with soap and water. I then like to rinse with clear hot water. I then run some MAP or other solvents through the rifle to make sure nothing is in the barrel. This is when I give it a good scrubbing with a bore brush.
After the MAP, I run patches of isopropyl alcohol alone. This will pull any moisture out of the barrel for the most part and any crud that the MAP pulled. I then use some dry patches and they will come out clean after just a few. You then have to use a quality gun oil, and oil that barrel. If you do not, I can tell you, the next time you run a patch in there in the future you will see flash rust on it.
Soap and water is still one of the best cleaners for black powder and other propellants......