Smith & Wesson Revolver changes in the Strain screw

February 17, 2026

Smith & Wesson has changed the design, length, and head-style of their strain screws several times over the last 70 years. These changes typically align with shifts in frame design (such as moving from "5-screw" to "3-screw" frames) or the transition from square-butt to round-butt grips.

Here are the primary milestones for these changes:

1. The Transition to 3-Screw Frames (1961)

The most famous change occurred in 1961, when S&W eliminated the "trigger guard screw" (the fourth screw). This moved the production from "4-screw" frames to the modern "3-screw" design. While the strain screw remained, the standardization of the frame assembly changed how internal parts were fitted.

2. The Head Style Change (Early 1990s)

Between 1990 and 1993, S&W transitioned from a "tall head" strain screw to a "thin head" (or low-profile) screw.

Old Style: Features a noticeably thicker, taller head.
New Style: Features a flatter head to allow for better clearance with various grip styles, particularly the synthetic grips that became standard during this era.

3. Square Butt vs. Round Butt Lengths

While not a "date-specific" change for the entire company, the length of the screw changes based on the frame's grip profile.

Square Butt: Typically uses a longer screw (approx. 0.60" – 0.64").
Round Butt: Uses a shorter screw (approx. 0.48").
As S&W phased out most square-butt frames in the mid-1990s (standardizing almost everything to round-butt), the shorter strain screw became the factory standard for most models.

4. Modern MIM and X-Frame Era (2000s)

With the introduction of the massive X-Frame (.460 and .500 S&W) and the widespread use of Metal Injection Molded (MIM) parts, specific strain screws (like part #416790000) were created to handle the increased tension requirements of these larger revolvers.

Summary Table

Era	Change Description	Key Identification
Pre-1961	5-screw and 4-screw designs	High collector value; hand-fitted screws.
1961	Transition to 3-screw frames	Standardized K, L, and N frame screws.
Early 1990s	Head Profile Change	Moved from "Tall Head" to "Thin/Flat Head."
Mid-1990s	Frame Standardization	Shift toward Round Butt (shorter) screws.

Pro-Tip: If you are replacing a screw, always check if your frame is a "Square Butt" or "Round Butt," as using the wrong length will significantly impact your trigger pull and primer ignition reliability.