65 grain T7 3f Velocity Equivalent to Other Powders
The original post asks, "Any guesses on FPS leaving the muzzle with 65 grains?" Some replies offer guesses about the equivalent "Black Powder charge" this represents.
I tried to take this up with data. I didn't find Hogdon data for the the 460 No Excuses. The most similar lead conical offering where I found data from a common source for all of: Pyrodex and T7, 2f and 3f; is the 385 Hornady Great Plains bullet. From that data, I have estimated velocity for the 385 GP with 65 grains volume T7 3f, and then estimated the equivalent charge of various other powders to produce that same velocity. For BH 209, I used data that Western Powder published prior to removing such conical data from their site.
Method: Velocity for T7 2f & 3f, and Pyrodex RS & P, at 80 and 100 grains, is from Hogdon. Those velocities are then converted to energy. Then, energy is interpolated and extrapolated linearly from 65 to 100 grains. Those energy results are then converted back to velocity. I extrapolated energy because that seems more likely to vary linearly with powder charge, an energy source, rather than velocity that has a "squared" relationship with energy. I checked extrapolating velocity and the results across this range vary by only a few grains.
Result: This work shows that 65 grains T7 3f produces the same velocity as 86.5 grains Pyrodex RS, estmated as 1343 fps & 1542 ft-lb. The results are attached as <<T7 3f Conical3.pdf>>.
Confirmation: "Shooting range" confirmation is limited. I have used this method to estimate "sweet spot" charge for my rifle and several known loads when changing powders. I have found that the method seems to accurately predict accuracy sweet spots for my loads and gun. I do not have actual velocity data, but the method saves me a lot of time when changing powder.
While this work doesn't provide a "velocity" for the 460 NE, it may be a guide to equivalent powder charge, 65 T7 3f being approximately equivalent to 87 RS. The energy of 1542 ft-lb, may be similar to the 460 Ne. At 460 grains, 1542 ft-lb energy converts to 1229 fps.
The heavier 460 NE probably produces more energy, than the 385 GP. White Muzzleloading publishes data for the 460 PowerPunch, using Pyrodex P. I performed a similar analysis using that data and more data manipulation to create results for the other powders. Those manipulations may be a stretch of physics, so I'll just provide the result without explanation: 65 T7 3f with 460 conical estimated as 1316 fps, 1770 ft-lb, and equivalent to 92.4 grains Pyrodex RS.
txhunter suggested adding 8 - 10 grains to get to a "black" equivalent. Maybe this is using the T7 "15%" suggestion? I think the "15%" approximation is for adjusting 2f to 2f and 3f to 3f, not for going from, say 3f of one product to 2f of another product. 2f T7 to 3f T7 can be 14% on its own. I also think the 15% is more about pressure (safety) than velocity. A feature of T7 is that it produces more velocity for a given pressure than Pyrodex (or Black). So, the powder adjustment for equivalent velocity is more than 15%. Using the published velocity data should be better.
Several experts have offered that 80 - 90 grains is a good elk load. If 65 T7 3f is equivalent to 81 Pyrodex P or 87 RS, it seems to meet the load suggestion.
Maybe someone can confirm this with some chronograph work.