Hello:
Fascinating stuff.
I have three different lots of STARLINE 50-90 SHARPS brass and each has the same rim OD of .660" and body OD at rim of .559" - .560".
I see the Wiki dim for 50-90 Sharps of .585", but there is no longer a SAAMI drawing for the 50-90 Sharps. Per Howell on page 407, the 50-70 Gov'.t base at rim OD is .570", but he noted a .568" variation.
Based on my three lots of Starline 50-90's, you might want to verify 50-90 dim's with Hunter Pilant, Process Mgr and Chief Ballistician, hunter@starlinebrass.com.
Please keep us posted. Thanks and smiles.
El Supremo/Kevin Tinny