Trail boss velocity/pressures compared to standard powders

[condor bravo]

Loading manuals carry limited Trail Boss loading data by grains, restricted to those calibers considered most likely to be used with cowboy action shooting. The Lyman cast bullet handbook shows several vintage rifle loadings with cast bullets along with some handgun calibers. A comparison of the velocity/pressure figures with TB and compared to those with standard powders is interesting and perhaps contrary to what might be expected. From the Lyman manual and using the .30-30 as an example, 8.0 to 8.5 gr TB indicates velocities from 1054 to 1102 and pressures from 31,300 to 37,400 with a 173 gr cast bullet. Other powders such as Unique, Herco, 2400, 4227, 4198 and a host of others all display velocity increases up to 1000 fps and with pressures up to 6000 psi less, and less for any loading. Interesting. Is the 8.5 gr TB a max load as derived from Hodgdon's formula? Not hardly it seems. I just checked a Remington case filled to the base of a 170 gr cast bullet and the grain weight was right on at 11 grains for Hodgdon's max load formula.

A more comprehensive loading manual showing similar figures for TB powder with modern cartridges might be desirable.

 

[T. O'Heir]

"...6000 psi..." Hodgdon gives TB data with CUP pressures, not PSI. There is no mathematical conversion. Or comparison. So no, Lyman, who do their own tests unlike Lee, is not using Hodgdon data. And there is no formula.
Suspect there is no TB data because it is designed as a cast bullet powder. Isn't a lot of cast bullet data much of anywhere. Not enough demand.

 

[condor bravo]

Yes, you are right, CUP not PSI pressures for all the .30-30 loadings listed (handgun pressures shown as psi however). So modify the 6000 psi statement to read 6000 cup. But the conclusion overall is that you are gaining more velocity and less pressure with standard powders than with what might be considered "equivalent" or appropriate loads of TB. The difference between starting and max loads with the "other" powders is only two grains in some instances. While TB was initially developed for cowboy action shooting and cast bullets, it is now also used considerably with more modern calibers and even jacketed bullets rather than just being confined to .38-55 Winchester et al types.