{"product_id":"sw-k-frame-mp-1st-model-4-screw-bolt-spring-plunger-38-colt-mpc4","title":"S\u0026W K Frame M\u0026P 1st Model 4-Screw Bolt, Spring \u0026 Plunger .38 Colt – Part# MPC4","description":"\u003ch2\u003eSmith \u0026amp; Wesson K Frame Military \u0026amp; Police 1st Model Bolt, Spring \u0026amp; Plunger – 4-Screw, Old Style\u003c\/h2\u003e\n\n\u003cp\u003eA rare factory-original bolt, spring, and plunger set for the earliest production K Frame revolvers. This part was sourced from a Military \u0026amp; Police 1st Model revolver (Serial# 3312) chambered in .38 Colt — one of the earliest S\u0026amp;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.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e MPC4\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFits:\u003c\/strong\u003e Smith \u0026amp; Wesson K Frame Military \u0026amp; Police 1st Model (4-Screw)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCaliber:\u003c\/strong\u003e .38 Colt\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eIncludes:\u003c\/strong\u003e Bolt, Bolt Spring \u0026amp; Bolt Plunger\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eEra:\u003c\/strong\u003e 4-Screw, Old Style\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFinish:\u003c\/strong\u003e Blue Steel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eProvenance:\u003c\/strong\u003e Sourced from Serial# 3312\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCondition:\u003c\/strong\u003e Used (factory original)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInstallation:\u003c\/strong\u003e Gunsmith fitting recommended\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eFactory Replacement Quality\u003c\/h3\u003e\n\u003cp\u003eGenuine Smith \u0026amp; 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.\u003c\/p\u003e\n\n\u003ch3\u003eAbout the M\u0026amp;P 1st Model\u003c\/h3\u003e\n\u003cp\u003eThe Military \u0026amp; Police 1st Model (introduced circa 1899) was one of the first S\u0026amp;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.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eQuestions?\u003c\/strong\u003e Call or email us — we're happy to help you get the right part the first time.\u003c\/p\u003e","brand":"Smith \u0026 Wesson","offers":[{"title":"Default Title","offer_id":40853771518010,"sku":null,"price":24.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1423\/2020\/files\/s-l960_1_45658cd0-08a2-4164-84d5-90eb46bf22da.webp?v=1745340483","url":"https:\/\/usagunsandgear.com\/products\/sw-k-frame-mp-1st-model-4-screw-bolt-spring-plunger-38-colt-mpc4","provider":"USA Guns And Gear","version":"1.0","type":"link"}