Quote Originally Posted by dogmower View Post
The rule of thumb I've been taught is that if you load IMR4198 at 0.3 times the weight of the original blackpowder load, you should be safe and in the same ballpark, pressure wise.
So, if the original load was say, 85 grains of BP, the smokeless load would be 0.3x85, or 25.5 grains. FWIW, this formula has worked well for me in the 577/450 martini and the snider enfield, as well as the Dutch Beaumont and the 71/84 mauser.
If that is correct that comes to 16.5 gr; you are saying this should be safe on pressure and about the same velocity as the original black powder load?

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