jdbe,
You will find that 777 does leave fouling, but it breaks up much easier than the Pyro fouling does. When spit patching between rounds, I've found that 3 patches will pretty much remove all fouling - but when continuing to shoot, I only run 1 patch between rounds.
Now with my Knight, 777 DOES tend to gum up my breech plug - and pretty badly at that. I still use #11cap ignition, so the common recommendation to loosen the plug every few shots to make sure it doesn't freeze doesn't work for me as I'd have to remove the nipple everytime to do it. I've tried every grease, anti-sieze, etc I could find and the only grease product that come close to working is CVA's Slick Breech Plug & Nipple grease - but after about 20 shots, even it fails to prevent seizing. The only 100% surefire cure I found is using the T/C Breech Plug Tape (or a Generic heavy duty Teflon equivalent) - this has never failed to work and it is actually easier to clean out of the threads than any of the greases, so it isn't a bad thing to use anyway.
777 is definitely more powerful than Pyro, by 10 to 15%. Your 110gr Pyro load will probably only need 90gr of 777 for equivalent performance. Based on my average rifle load, you can figure on 6 to 10 more shots out of a one lb bottle of 777.