Hi Folks,
I wandered into this thread a late-comer, obviously. Having been nosing around in some reloading information lately, and always interested in the wisdom/perils of the oft-mentioned nitro-for-black loads, is should be mentioned that TrailBoss is a quite "fast" powder as far as its position on a list of smokeless powder burn-rates. In short, it tends to perform like a rapidly pressure-building pistol powder. Doubtless this is how it was designed, to give BP-like obturation to lead bullets for Cowboy Action and other shooting. Many other smokeless powders do not have a "quick" enough pressure curve to bump up (obturate) bullets like BP will do. BP goes off quickly once ignited (and it is EASILY ignited, as mentioned by others here), and provides obturation for good bullet function, lack of leading, and accuracy.

Trailboss didn't work, according to Sherman Bell in the Double Gun Journal (tireless experimenter if there ever was one), for use in large capacity BPE cases. No doubt it was simply "out of its league" as far as its design features. BP will work in all kinds of applications, notably by choosing the best granulation.
Now if Hodgdon will go a step further and make a "TrailBoss P" for pistols, similar in purpose to Pyrodex P, as well as a "TrailBoss RS" similar to Pyrodex RS for rifles and shotguns, we may be in business. They already have the TrailBoss P, or close to it, in the currently marked TrailBoss powder.

As an aside, Triple7 substitute powder is NOT just another Pyrodex. It is relatively not stuff, similar to Swiss BP as to pressure and power IMHO, and was developed for use in modern ordnance-steel MLs. It should not just be used willy-nilly for a BP substitute in old guns. Please keep in mind, too, that all these substitute powders, including Pyrodex, are really smokeless powders with some additives for smoke. So to say we never use smokeless powders in MLs is a misnomer. It is the KIND of smokeless, and its design parameters, that is critically important.

Aloha, Ka'imiloa