Evolution IV Revolver Hammer Kit

This is a pinned-sear replacement hammer kit designed to convert S&W J-frame, K-frame, L-frame, and N-frame revolvers to Double Action Only (DAO) operation while dramatically reducing pull weight. The factory MIM hammer assembly is replaced with a precision-machined hammer using a pinned sear and stirrup—the same architecture found on Performance Center revolvers. When properly tuned by an experienced revolver smith, this kit can drop a factory 12+ lb. DAO trigger pull to approximately 4.0 lbs. At that pull weight, handloads with light primers are recommended for reliable ignition. This is not a drop-in part; it requires fitting and timing work.

Compatibility

• S&W J-frame (Model 340, 640, 642, 442, etc.)
• S&W K-frame (Model 64, 65, 66, etc.)
• S&W L-frame (Model 686, 619, 620, etc.)
• S&W N-frame (Model 625, 627, 629, etc.)
• Not compatible with pre-MIM or lock-less frames without modification
• Converts existing revolver to DAO only—single-action capability is removed

Key Features

• Replaces factory MIM hammer with CNC-machined steel hammer, pinned sear, and stirrup assembly
• DAO conversion: hammer spur removed, single-action notch eliminated
• Target pull weight: ~4.0 lbs DAO after proper tuning (requires professional fitting)
• Reduced lock time and shorter hammer travel vs. factory hammer
• Performance Center-style pinned sear geometry for consistent engagement

Install Difficulty: 4 out of 5

This is not a drop-in component. Requires removal of the sideplate, trigger guard, and hand assembly. The hammer must be fitted to the frame and the sear engagement checked with a timing gauge. Sideplate screws must be staked. Tools needed: screwdriver set with hollow-ground bits, brass punch set, small hammer, timing gauge, stones or files for fitting. Strongly recommend installation by a certified revolver gunsmith.

FAQ

Will this fit my S&W 686-6+?

Yes, the Evolution IV Hammer Kit fits L-frame revolvers including the 686-6+. The pinned sear and stirrup design is compatible with the lockwork in these models. Verify that your revolver uses a frame-mounted firing pin—this kit is not intended for hammer-mounted firing pin guns.

Does the 4.0 lb pull weight require handloads?

At 4.0 lbs DAO, the hammer fall energy is reduced. Factory ammunition with hard primers may produce light strikes. Handloads using Federal, CCI, or Winchester small pistol primers (or equivalent) are recommended for reliable ignition. Test fire with your chosen ammunition before competition use.

Can I keep single-action capability?

No. This kit is designed as a pure DAO conversion. The hammer spur is removed and the single-action sear notch is eliminated. If you need a SA/DA revolver, this is not the correct component. For single-action use, consider a different trigger system.

Shipping: Ships within 1 business day via USPS Priority. Warranty: This component carries a limited lifetime warranty against manufacturing defects. Fitting and tuning work by the installer is not covered. Return for replacement if defective; no refunds on fitted parts.