Smith & Wesson K Frame Strain Screw - Models 17 & 18 - Square Butt - Blue Steel - Old Style - Used - .22 LR 173C

Factory OEM Smith & Wesson K Frame Strain Screw

Part Number: 173C
Compatibility: K Frame Models 17 & 18
Caliber: .22 LR (Rimfire)
Grip Type: Square Butt
Finish: Blue Steel
Style: Old Style
Condition: Used
Frame Size: K Frame

This is an authentic Smith & Wesson factory strain screw (also called a mainspring tension screw) for K Frame Models 17 and 18 revolvers with square butt grips. The strain screw adjusts the tension on the mainspring, which controls hammer fall and trigger pull weight.

Features:

• Genuine Smith & Wesson factory part
• Blue steel finish matches original factory specifications
• Square butt configuration
• Old-style design for early production models
• Used condition with functional threads
• Direct replacement for damaged or missing strain screws
• Allows adjustment of mainspring tension

Compatibility Note: Strain screws are interchangeable across all K Frame models with the same grip frame style (square butt vs round butt). This square butt strain screw will fit Models 10, 12, 13, 14, 15, 16, 17, 18, 19, 48, 64, 65, 66, 67, 617, and 648 that have square butt grip frames. It will NOT fit round butt models.

Function: The strain screw threads into the bottom of the grip frame and applies tension to the mainspring. Tightening the screw increases mainspring tension (heavier trigger pull, harder hammer fall), while loosening it decreases tension (lighter trigger pull, softer hammer fall). Proper adjustment is critical for reliable ignition.

Installation: The strain screw can be installed by the owner. However, proper adjustment requires knowledge of safe mainspring tension levels. Too little tension can cause light strikes and misfires; too much tension creates excessive trigger pull weight. Professional gunsmith adjustment recommended for optimal performance.

How to Identify Your Smith & Wesson Model: Swing out the cylinder and check behind the yoke on the frame for the model number. Model numbers began in 1957-58. If you need assistance identifying your revolver or confirming compatibility, contact us with your serial number.

Questions? Contact us at sales@usagunsandgear.com or call 770-544-8075. We specialize in Smith & Wesson pistol and revolver parts - new, used, NOS, and refurbished.