10-32 x .500 Alloy Low Head Cap Screw

10-32 x .500 Cap Screw, part #66009 — a factory replacement component for the RL1100 Primer Slide Stop / Case Eject Assembly.

Shown on page 69 of the RL1100 manual. Check the exploded diagram on that page against your machine to confirm this is the part you need before ordering.