Reggie - good-on-ya.
Trail Boss is being used a wide variety of rifle ctgs. these days. The boys at the small bore site I frequent are even using it in their .17's and .20's for plinking and go-spat, loads.

While it is quite safe in modern actions, especially singles and bolt guns, do note that it developes pressure higher than the older more typical low velocity squib loadings. By that I mean, it's easy to get it up to around 30,000PSI while only producing 900 to 1,200fps, in some ctgs.