Hollow base vs solid base data question

[LonesomePigeon]

I recently purchased MP Molds HG#50 HBWC 38. This is a mold that has inserts that allow it to make three different styles of bullets. A 148 grain wadutter with a solid base, a 128 grain hollow base wadcutter with a cup shaped hollow base and a 128 grain hollow base wadcutter with a cone shaped hollow base.

Looking at my Lyman Cast Bullet Handbook #4 I see .38 Special load data for a 148 grain solid base wadcutter. Can I use these same loads for a hollow base 128 grain wadcutter? Starting at the low end charges and working up to find the most accurate charge. I would be shooting them out of a .357 Magnum Colt New Frontier.

By the way, I shot some of these hollow base bullets with black powder. One thing I like about black powder is you don't need data, just fill the case up so there's a bit of compression and it's good.

[mtmarfield]

      Greetings!

   You should be safe using 148 gr. HBWC data; since your bullet is lighter than the standard, you should have no problems, although I wouldn't reduce 'starting loads'. Of course, you can contact your favorite Powder Company for a suggestion based upon your bullet description. Have Fun, and Keep Us Posted!

                   M.T.Marfield
                    12-10-22

[cpt dan blodgett]

You probably really do not want to attempt serious .357 Mag velocities betting you will find your most accurate some where down close to starting loads assuming your powder of choice is not position sensitive.  This is load development some where between fun and self torture but does get one hooked.