When you say only 52 grains are we speaking actual weight or volumetric weight?
If volumetric, I don't know how you can be so precise?
Actually, not to be a PITA but I wonder if you've read the litature that comes with 777?
Among other things it says:
"Triple Seven is a high energy product designed to provide the muzzleloading hunter with higher velocities when used in the same VOLUME as blackpowder. To duplicate a blackpowder load velocity using Triple Seven, you must decrease the powder charge by 15%. *See WARNING below.
Pyrodex is lighter in weight than blackpowder and weighs only about 70% as much as blackpowder. However, because Pyrodex yields more energy per pound than does blackpowder, the same volume of Pyrodex gives similar performance to blackpowder. Pyrodex loads given in this manual for muzzleloading guns are measured by volume, not weight."
That is saying to me that it is already 15 percent more powerful than black powder and it weighs 30 percent less (actual weight).
Hodgdon goes on to say about 777:
"...Do not heavily compress powder charges. The use of filler wads, inert fillers or heavy compression may cause a dangerous situation, which could cause injury and/or death to the shooter, bystanders or damage property."
IMO, messing with heavy, compressed loads of 777 is asking for trouble.
If the 52 grains is an actual weight of the 777 powder load it would be equal to 69 grains volume of black powder.
If it is 15 percent more potent than black powder that 69 grains equivalent has the energy of a 79.7 grain black powder load.
If it is heavily compressed under a heavy slug it is, in my mind totally OVERLOADED.
If you want to shoot magnum power loads go buy a .44 or .45 mag and have fun.
For folks who want to read Hodgdons full comments you can follow this link
Hodgdon 777 LOADING INFORMATION