{"product_id":"sw-k-frame-mp-1st-model-4-screw-strain-screw-38-colt-mpc9","title":"S\u0026W K Frame M\u0026P 1st Model 4-Screw Strain Screw .38 Colt – Part# MPC9","description":"\u003ch2\u003eSmith \u0026amp; Wesson K Frame Military \u0026amp; Police 1st Model Strain Screw – 4-Screw, Old Style\u003c\/h2\u003e\n\n\u003cp\u003eA rare factory-original strain screw 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 strain screw threads into the grip frame and controls the tension on the mainspring — adjusting it affects trigger pull weight in both single and double action. Correct-era parts for these early 4-screw revolvers are extremely difficult to find.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e MPC9\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\u003ePart Type:\u003c\/strong\u003e Strain Screw\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\u003eStrain Screw \u0026amp; Trigger Pull\u003c\/h3\u003e\n\u003cp\u003eThe strain screw is one of the few user-adjustable components on a S\u0026amp;W revolver. Backing it out slightly reduces mainspring tension and lightens the trigger pull — however, this can also cause light primer strikes. Always verify reliable ignition after any adjustment. Gunsmith guidance is recommended, particularly on these early revolvers where parts tolerances differ from later production.\u003c\/p\u003e\n\n\u003ch3\u003eFactory Replacement Quality\u003c\/h3\u003e\n\u003cp\u003eGenuine Smith \u0026amp; Wesson factory part from the correct production era — same thread pitch, same dimensions, same reliable mainspring tension control. 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":40859083079738,"sku":null,"price":9.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1423\/2020\/files\/s-l960_39_4673ff2d-7f50-47f6-8aa7-7d38f9ee8306.webp?v=1745860538","url":"https:\/\/usagunsandgear.com\/products\/sw-k-frame-mp-1st-model-4-screw-strain-screw-38-colt-mpc9","provider":"USA Guns And Gear","version":"1.0","type":"link"}