August and Grits are right. For the reduced lighter loads in 38 Spec you want for your son, there are a whole variety of powders available that would have 'much' better results. As indicated by August, blue dot is a slower burner than what you need. Of the 118 powders available listed in most reloading manuels, blue dot is listed as number 41. Another one of Alliant's powders, 2400 is num 45, Winchester's 296 is number 51. Both of these powders are used for higher velocity/magnum loads. So you can see that Blue Dot isn't that far from being considered a powder to be used for magnum load considerations. I've always used Blue for jacketed 1000fps plus loads in 357 loads. In some of my reloading info source's, many don't even list using Blue Dot for 158 g lead bullets. I've never used Trail Boss in 38 loads, using it in 45 Colt, but it should work well. Titegroup, Winchester 231, Hodgon HP38 are all good powders that I've used in 38 Spec with cast 150 grain SWC in various loadings and all worked very well.