Can you guys suggest a medium load for my 3" Ruger SP-101 using:

158 LRN BB (Carrol 38158)
Unique or Clays
Winchester brass
CCI 550 Small Pistol Magnum primers

and, suggest a more suitable powder for same bullet?

I'm pretty sure I'll end up getting another powder but am hoping to use my 45 ACP component if possible.

This will be my first 357 mag reload.

BTW, these 158 gr bullets look puny.

So far, I've only loaded 45 ACP and 45-70 Govt.

First let me make sure we are on the same page. You are useing plain 158gr lead round nose bullets if so Ihave used Unique 5.5 - 6.0gr with cci 500 small pistol. You won't need magnum primers with this load. Shooting lead bullets you want to keep speed down not to lead berral up to much. Unique also works well in 125gr jacked 8.6 - 9.6 also cci 500 primer. Both loads I have used & are out of the Speeer manual #13. Get your self a good Manual you will be suprised if your not useing ball powders or heavey loads you will not have to use magnum primers all that much.

Generally speaking, magnum primers are only needed for the slowest burning powders. These would be W-296, H-110, AA#9, maybe Alliant 2400.

Lymans 47th on page 390 shows that they used CCI 550 Small Pistol Magnum primers exclusively. So that's what I bought.

I've been using Hodgdon's Titegroup in both .45 ACP and .357 magnum. You only use a little, but it is "position insensitive." It won't work for the hottest magnum loads, but works well for medium loads. I use my .45 ACP for monthly pistol matches, with 5.0 gr of Titegroup and a lead 200 gr bullet. I'll have to check on the load I'm using in the .357.