{"product_id":"sw-k-frame-model-66-strain-screw-square-butt-357-magnum-64173","title":"S\u0026W K Frame Model 66 Strain Screw Square Butt .357 Magnum – Part# 64173","description":"\u003ch2\u003eSmith \u0026amp; Wesson K Frame Model 66 Strain Screw – Square Butt, Old Style\u003c\/h2\u003e\n\n\u003cp\u003eFine-tune your trigger pull on your Model 66 with this factory-original strain screw. 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. This old-style square butt stainless steel screw is the correct replacement for the Model 66 Combat Magnum chambered in .357 Magnum.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e 64173\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFits:\u003c\/strong\u003e Smith \u0026amp; Wesson K Frame Model 66 (Square Butt)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCaliber:\u003c\/strong\u003e .357 Magnum \/ .38 Special\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePart Type:\u003c\/strong\u003e Strain Screw\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eStyle:\u003c\/strong\u003e Old Style\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMaterial:\u003c\/strong\u003e Stainless Steel\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFrame:\u003c\/strong\u003e Square Butt\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 part manufactured to the exact specifications and tolerances of the original — same thread pitch, same dimensions, same reliable mainspring tension control. No aftermarket substitutes.\u003c\/p\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.\u003c\/p\u003e\n\n\u003ch3\u003eFinding Your Model Number\u003c\/h3\u003e\n\u003cp\u003eSwing out the cylinder and check behind the yoke on the frame. Model numbers have been stamped there since 1957–58. If your revolver predates that, contact us with the serial number and we'll help identify the correct part.\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":40868505354298,"sku":null,"price":4.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1423\/2020\/files\/s-l960_37_d6173417-eaca-4274-a9f9-d3744bbb35f6.webp?v=1746808492","url":"https:\/\/usagunsandgear.com\/products\/sw-k-frame-model-66-strain-screw-square-butt-357-magnum-64173","provider":"USA Guns And Gear","version":"1.0","type":"link"}