I think they were both involved as was Wesson, but Sharpe is seldom mentioned as one of the .357 Magnum developers for some reason. Many are unaware of this. Sharpe also designed the original and perhaps the best .357 Magnum bullet, the Hensley & Gibbs #51, a 160 grain plain base cast SWC.
IMHO:
The H&G #51 is 1 of the poorest/worst designed 357mag bullets ever invented.
I did head to head testing with these 357mag bullets in several different fire arms. Used 3 different alloys along with testing them in 38spl p+ loads also.
Bottom right is a h&g #51 hp Had a 2 cavity mold that cast a swc and a swc hp.
That H&G #51 bullet consistently gave up (less fps) 50fps to 70fps compared to the other bullets pictured (5 different powders/10 bullets tested) in 38spl p+ loads. The H&G #51 gave up/had less then 100fps with hot 357mag loads compared to the other bullets pictured above.
Tried different alloys, sized to .357/.358/.359" nada, just a poor design. Namely the small bottom drive band, huge/long grease groove and 2 small top drive bands.
A close-up of common cast swc bullets. As you can see other bullets have the small bullet base/small bottom drive band. The difference is the rounded/stronger grease groove. The plain bullet to the left of that h&g #51, the cramer #26 has a huge bullet base/bottom drive band.
Same loads, alloys, firearm, shooter, chrony, yada-0yada-yada. That cramer bullet ran circles around the h&g #51 with up to 70fps faster in 38spl p+ loads and 100fps faster with 357mag loads. The cramer also had better accuracy.
These 4 bullets consistently out preformed the other 6 bullets pictured above including the worst performing h&g#51.
What they have in common is strong large bottom drive bands or a gc that seals the pressure of the heavy loads faster. Along with bullet bodies that have large percentages of them sealing the bbl also. This makes these bullets more efficient, hence higher velocities with the same loads.