Although 777 does indeed claim to produce about 15% more velocity and one would assume pressure then an equivalent charge of Pyrodex P, I simply load a tad less 777 when I am using it, so I break about even on velocity and I assume wear and tear.
I generally use a sput that throws about 28 grain for Pyrodex and one that throws around 24 for 777 with no problems thus far. I have found 777 to be a bit cleaner to clean up then Pyrodex and you use less per shot, so not all bad..just my opinion tho, I could be wrong.
I see your point. If reduced 15%, as recommended, perhaps it is a wash. What caught my attention was that the 35 gr. max load of Pyrodex P produced a higher velocity, whereas the 25 gr. max load of 777 a lesser velocity. I drew some conclusions from that, though I don't know they are correct.
1. Even though 777 is intended to produce more energy, it may produce it with pressures that prevent using that potential in a repro revolver.
2. Because the max load is less than Pyrodex P *and* the velocity is less I get the feeling the pressures (and possibly temps) are significantly higher, but with no gain in effectiveness for it's use. That I'd be better off in terms of killing power, to use the Pyrodex P and accept that a greater volume will be neccessary. Not a new phenomenon. Smokeless Bullseye or even Unique compare to 2400 when used in a .44 mag in the same way.
3. Perhaps the real intended use for 777 is in guns designed to actually withstand it's use. Say 209 inlines and the like.
I wish manufacturers would just come out and say these things though, rather than leaving us to guess.
Given my goal is to maximize the on target effectiveness while staying within the gun's limits, I'm thinking the Pyrodex P option is the better choice. Whereas, if I was looking to use less powder for just target shooting, maybe 777 would be the better choice. Same rationale as making target loads with Bullseye with 3 gr. of powder but hunting loads with 20 grains of 2400. IIRC 20 grains of Bullseye would be seriously over pressure in a .44 mag.
But you get the idea. Bullseye is so "hot" you can't use much of it, and this limits the ultimate velocity you can achieve. 2400 is more progressive and slower burning, so, though you have to use more of it... you can get a higher ultimate velocity out of it. Or so I believe anyway.
Seems 777 is in that same category. Unless I exceed Hodgdon's recommended 25 gr. I can't get the same velocity at Pyrodex P.
For me personally, I'm thinking that makes it an incorrect choice since the intended use of the gun is hunting rather than paper punching.
Sound like I'm barking up the wrong tree?
P.S. Anyone have any experience leaving a revolver loaded with 777 for long periods? I'm wondering if it's composition is inherently corrosive? I've read in the forums here of folks sealing standard black with beeswax and not having corrosion problems. But I believe I once read 777 is citric acid based? Sounds like a bad combination with gun steel.