First off, HS6 with a 125 xtp was accurate in my 686 6"........

6" barrel standard load at 1037fps.
2" M49 standard load came out at 867fps.

CFE at 862fps, w231 at 840, Unique at 870fps for standard loads.
With a full load 800-x, Red & Green Dot and Unique powders can reach 900fps in my snub nose.
However, even with this high fps, I do not use this weigh/style of
bullet for my SD use in the M49.
I did like the accuracy when one full grain less than my maximum loading.
Good shooting.