I am wonder what the difference is between ffg powder and fffg powder. Also what is the maximum load using powder(not pellets) in a muzzleloader rated for 150 grains.

fff is typicaly for pistols, faster buring, little hotter.
ffis typicaly for rifles.

Need to know what rifle you have first before we can tell you what kind of loose powder charge it will accept.

It is generally accepted that 777 is about 15% stronger [more potential energy] it is also faster burning which increases the pressure faster, I personally dont normally use more than 110gr in a rifle rated for 150 of black powder or pyrodex but I have a friend that is using up to 120 so far he has not had a problem.
AS for the differance between FF and FFF it changes with what powder you are talking about with 777 there does not appear to be as much differance as there is in other powders.Lee

fffg is finerthan ffg,if your using loose triple 7 loose powder dont go over 110 grains .

If you look at the velocity of the two powders there is really not all that big a difference between the ffg and the fffg. FFFg is a fine grade, burn faster creating more pressures in the barrel. Your rifle might like it. All you can do it try it. I like the FFFg when shooting conicals. FFg shoots sabots just fine for me.

The max load of loose powder in your inline rifle is around 100-120 grains depending on the make of the rifle. I would not go over 120 grains of Triple Se7en. Be sure and check your owners manual for the actual recommendations of the manufacturer.

i will be using a traditions lt 50 cal muzzleloader.