Smith & Wesson Revolver J Frame Mainspring/Hammer Spring All Models - Factory New OEM - 071040000

Genuine Smith & Wesson J Frame Mainspring - Multi-Model Compatibility

Factory new OEM mainspring (hammer spring) designed for all Smith & Wesson J Frame revolvers. This critical internal component provides the force needed to drive the hammer forward and strike the firing pin, ensuring reliable ignition with every trigger pull. Compatible with virtually all J Frame models from vintage to modern production.

Key Features:

• Genuine OEM Part: Authentic Smith & Wesson factory component, not an aftermarket substitute
• Universal J Frame Fit: Compatible with all J Frame models (see extensive compatibility list below)
• Critical Fire Control Component: Provides proper hammer strike force for reliable ignition
• Factory New Condition: Brand new, never installed, ready for immediate use
• Precision Manufactured: Meets Smith & Wesson's exact specifications for spring tension and durability
• Heat-Treated Spring Steel: Engineered for consistent performance and long service life

Extensive Model Compatibility:

This mainspring fits all Smith & Wesson J Frame revolvers, including but not limited to:

Models: 30, 31, 32, 33, 34, 35, 36, 37, 38, 40, 42, 43, 49, 50, 51, 60, 63, 317, 331, 332, 337, 340, 342, 360, 431, 432, 437, 438, 442, 460, 631, 632, 637, 638, 640, 642, 649, 651, 940

Note: This mainspring is compatible with both centerfire and rimfire J Frame models, making it one of the most versatile internal parts in the J Frame lineup.

Part Number:

Smith & Wesson Factory Part Number: 071040000

What is a Mainspring?

The mainspring (also called the hammer spring) is the powerplant of your revolver's fire control system. When you cock the hammer or pull the trigger in double-action mode, you compress the mainspring. When the sear releases, the mainspring drives the hammer forward with enough force to strike the firing pin and ignite the primer. A worn or weakened mainspring can cause light primer strikes, misfires, or failure to fire, especially with hard primers or in cold weather.

Signs You Need a New Mainspring:

• Light primer strikes or occasional misfires
• Inconsistent ignition, especially with certain ammunition brands
• Noticeably lighter trigger pull than when new
• Visible wear, corrosion, or damage to the spring
• Revolver has been in storage for extended periods

Why Choose Genuine OEM Parts?

When it comes to critical fire control components like mainsprings, genuine Smith & Wesson OEM parts ensure proper spring tension, heat treatment, and material specifications. The mainspring must provide exactly the right amount of force—too weak and you'll get misfires, too strong and the trigger pull becomes excessively heavy. Smith & Wesson mainsprings are precision-manufactured and tested to deliver consistent, reliable performance for thousands of cycles.

Fast shipping on all in-stock Smith & Wesson parts. Order today to restore your J Frame revolver to factory specifications.