S&W K Frame M&P 1st Model 4-Screw Bolt, Spring & Plunger .38 Colt – Part# MPC4

Smith & Wesson K Frame Military & Police 1st Model Bolt, Spring & Plunger – 4-Screw, Old Style

A rare factory-original bolt, spring, and plunger set for the earliest production K Frame revolvers. This part was sourced from a Military & Police 1st Model revolver (Serial# 3312) chambered in .38 Colt — one of the earliest S&W hand ejector revolvers ever produced. The bolt (cylinder stop bolt) works in conjunction with the cylinder stop to index and lock each chamber in line with the barrel at the moment of firing — a worn or damaged bolt leads to cylinder timing issues and inconsistent lockup. Correct-era bolt assemblies for these early 4-screw revolvers differ in geometry from later production and are extremely difficult to find.

• Part Number: MPC4
• Fits: Smith & Wesson K Frame Military & Police 1st Model (4-Screw)
• Caliber: .38 Colt
• Includes: Bolt, Bolt Spring & Bolt Plunger
• Era: 4-Screw, Old Style
• Finish: Blue Steel
• Provenance: Sourced from Serial# 3312
• Condition: Used (factory original)
• Installation: Gunsmith fitting recommended

Factory Replacement Quality

Genuine Smith & Wesson factory parts from the correct production era — same dimensions, same cylinder timing geometry, same reliable lockup. On these early 4-screw revolvers, bolt geometry differs from later K Frame production — always verify fit before installation. Correct-era parts for these early revolvers are increasingly scarce.

About the M&P 1st Model

The Military & Police 1st Model (introduced circa 1899) was one of the first S&W swing-out cylinder revolvers and the direct ancestor of the legendary Model 10. Early production revolvers like Serial# 3312 predate the model number system by decades — if you're unsure whether this part fits your specific revolver, contact us with your serial number and we'll help confirm compatibility.

Questions? Call or email us — we're happy to help you get the right part the first time.