The mags are called for with H110 and Lil Gun, but some years back tests showed erratic results with 2400. The results were published in HANDLOADER IIRC. All .357 data in the Alliant handbook is with standard primers. Check out the data on Loaddata.com (you don’t need to sign up to see primers,OAL etc). I just took a peek and their data uses standards except for the two mentioned plus another, A-11 FS.
Do what you have to, but be aware and careful.
The Speer manual of a few years ago changed their primer recommendation with Alliant 2400. They found more consistent results using standard pistol primers vs. magnum.
