Trail Boss does some really weird things in terms of pressure. I would avoid it in old firearms meant for black powder. Don't assume it's low pressure just because it's low velocity.
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here is the thing with trail boss ...... is was designed to flash up to max pressures rather quickly , then taper off rather quickly .
the reason for this is to provide a safe low velocity powder .
the pressure spike is not unsafe , it actually is something very desirable when making low velocity ammo .
the reason being you get max pressure right away , and you get the bullet up and moving at full steam without hesitation , just like a normal or high pressure loading .
but after the bullet is moving , the pressure drops back providing the low velocity .
the advantage of this is no stuck bullets in barrels , no detonation and no secondary pressure spikes ...... and what I really like , because it is bulky , no double charges that can make your gun a hand grenade .
things like this can happen when doing low velocity loadings with other powders .
when your using it , follow the reloading info carefully . imr provides the amount of pressure to expect with each loading . it is also a easy powder to estimate pressure too . if the pressure is too much for the gun you have , you have some choices to make .
I have been using it for awhile and it is a absolutely wonderful powder for subsonic loadings .
and lately I have been finding it almost perfect for my French 1873 in 45schofield .
