Titegroup is a medium powder (think .38 Special) and you can load all the .357 you want, but only at "midrange" speeds as shown in the Hodgdon charts. You do not need magnum primers for Titegroup, but Hodgdon arbitrarily chose it for loading .357, which is OK but not necessary. The primer choice is based on the powder, not the case it is in. I use only SPP for Titegroup.
Titegroup is one of the most popular powders for action pistol competition in .38, 9mm and .40 S&W. It will not produce true magnum velocity in .357 cases nor would I expect it to. On the other hand, it is much more pleasant to shoot in short barrels, without the horrendous blast and fireball of 296.
