Underclocked1
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This was put together by a fellow with the handle of "Twanger" a few years back. "Twanger", aka Walt, is a physicist and came up with this chart after compiling a lot of data.
The chart is based upon a White M97 but should work to yield a close approximate muzzle velocity for about any non-smokeless muzzleloader of reasonable barrel length. It was also based upon the powder being Triple7 FFg so if your powder is hotter or milder than the T7 FFg, you should make a guestimated adjustment to your actual charge weight. For example, if you are shooting Blackhorn 209, you might wish to increase the value of your true load volume by 10% or so to accommodate the hotter powder.
Divide the VOLUMETRIC amount of your powder charge (in grains) by the actual weight of your projectile (in grains). That should yield some decimal value. Find the spot on the lower axis that corresponds to that decimal value and from there go straight up to the blue curve. From the point of the intersection with the blue curve, go directly to the left and find your velocity value.
For example, if your charge is 100 grains VOLUMETRIC of Triple7 FFg and your bullet weight is 250 grains, the resultant decimal fraction would be .40 . Go straight up from the .4 mark on the graph to the point on the blue curve, then read the velocity directly to the left on the vertical axis. You should get ~1850 fps and that should be within a very close ballpark of your actual velocity with that load.
There is also a curve for a White Javelina pistal which had an overall barrel length of ~14". Note that it is calculated based upon use of Triple7 FFFg. That curve should be useful for not only the Javelina, but for the Knight and CVA single shot pistols as well (and perhaps others).
The chart is based upon a White M97 but should work to yield a close approximate muzzle velocity for about any non-smokeless muzzleloader of reasonable barrel length. It was also based upon the powder being Triple7 FFg so if your powder is hotter or milder than the T7 FFg, you should make a guestimated adjustment to your actual charge weight. For example, if you are shooting Blackhorn 209, you might wish to increase the value of your true load volume by 10% or so to accommodate the hotter powder.
Divide the VOLUMETRIC amount of your powder charge (in grains) by the actual weight of your projectile (in grains). That should yield some decimal value. Find the spot on the lower axis that corresponds to that decimal value and from there go straight up to the blue curve. From the point of the intersection with the blue curve, go directly to the left and find your velocity value.
For example, if your charge is 100 grains VOLUMETRIC of Triple7 FFg and your bullet weight is 250 grains, the resultant decimal fraction would be .40 . Go straight up from the .4 mark on the graph to the point on the blue curve, then read the velocity directly to the left on the vertical axis. You should get ~1850 fps and that should be within a very close ballpark of your actual velocity with that load.
There is also a curve for a White Javelina pistal which had an overall barrel length of ~14". Note that it is calculated based upon use of Triple7 FFFg. That curve should be useful for not only the Javelina, but for the Knight and CVA single shot pistols as well (and perhaps others).
