Is 150 grains of Pyrodex RS equivalant to 150 grains of pyrodex pellets, or do I need to reduce the load by 15% like with the 777 ffg?

yes the Pyrodex is basically even across the board. The problem come in when you have Triple Se7en loose VS pellets...

You should still reduce your loose powder load to a maximum of 100-120 grains... whatever is detailed in your ML owners manual--simply because loose powder exhibits more bore pressure than pelletsin volume measurements - witha majority of ml bores.That's why so many manufacturers ask/recommend only 100-120 grains of loose -- yet allow higher volume 3-pellet (150 gr loads).

Loose powder is more compact than pelletswhich containfiller material to make them stay molded. Plus... loose powder compresses against all bore wall surfaces (360 degrees)-- unlike pellets in a majority of Mls. Slightly wider bore MLsmay only get 180 degree bore wall compressions with Hodgdon pellets.... slight gaps on any given two sides.

Also... loose powder can be easily tamped with the ramrod-- creating even-higher bore pressures/energy/speed. Pellets generally need to be more delicately seated - plus have a center hole in each pellet that despite slightly reducing pressure,the holes createaddedburn with ignition.

I have been under the impression that a volume measure of Pyrodex RS will produce higher velocities and pressure than will a "comparable"number of "grains" of Pyrodexpellets. However, I don't recall where I got thisidea, nor have I personally tested it by shooting both types to see what happens.

As a matter of fact, I don't shoot pellets at all, much preferring to be able to measure out a precise amount of whatever powder I'm using.