Trail Boss

[B.L.E.]

With 84 grains (weighed on scale) or 120 (Volumetric Units) of Black Horn 209 will push a 180 gr. HP/XTP at 2,227 FPS, what kind of pressure is being produced with this compressed powder charge? This is being shot from a modern muzzleloader.

My guess is 15,000 to 20,000 psi based on actual measurements of black powder pressures done by Lymann.
They also measured around 7,000 lup (lead units of pressure) in a special pressure cap and ball revolver.

The pressures of heavy black powder loads and light smokeless loads actually overlap to some extent. A lot of target shotshell loads only develop around 8,000 to 10,000 lup with smokeless.

 

[Brian Pfleuger]

IIRC, I believe that a modern inline ML typically maxes out in the neighborhood of 30,000 psi.