Evolution IV Revolver Hammer Kit

The Evolution IV Revolver Hammer Kit replaces factory MIM hammer, sear, and stirrup assemblies with pinned, precision-ground components. Designed for shooters converting a factory double/single action Smith & Wesson revolver to Double Action Only (DAO). This kit addresses the heavy, inconsistent trigger stack common in factory J, K, L, N, and X-frame revolvers by substituting the pinned sear and stirrup geometry found in Performance Center hammers. When properly fitted, the Evolution IV reduces DAO pull weight from 12+ lbs. down to approximately 4.0 lbs. — suitable for competition or precision handloading work. The conversion eliminates single-action capability entirely.

Compatibility

• Smith & Wesson J-Frame (models 36, 37, 42, 60, 63, 640, 642, 940 — excludes 340PD/360PD Scandium)
• Smith & Wesson K-Frame (models 10, 13, 14, 15, 17, 19, 64, 65, 66, 67, 617)
• Smith & Wesson L-Frame (models 586, 686, 619, 620)
• Smith & Wesson N-Frame (models 25, 27, 28, 29, 57, 58, 625, 629, 657, 686+ — excludes 329PD)
• Smith & Wesson X-Frame (models 460, 500 — verify fit with your specific dash number)
• Does NOT fit pre-MIM (pre-1997) S&W revolvers or Colt/Ruger revolvers

Key Features

• Pinned sear and stirrup assembly — eliminates MIM tolerance stacking
• Converts factory SA/DA to DAO only
• Drop-in replacement for factory hammer, sear, and stirrup (minor fitting may be required)
• Reduces DAO pull weight from 12+ lbs. to ~4.0 lbs. with proper tuning
• Includes Evolution IV hammer, pinned sear, stirrup pin, and installation instructions
• Material: 4140 steel, heat-treated and black-oxide finished
• Made in USA

Install Difficulty: 4/5

Requires revolver disassembly, hammer block removal, and sear/stirrup pin fitting. Tools needed: roll pin punch set (1/16″ and 3/32″), nylon hammer, bench block, small flathead screwdriver, and a vise or press for pin seating. Recommended for experienced revolver armorers. Expect 45–90 minutes for first installation.

FAQ

Will this work with my factory trigger return spring?

Yes — the kit uses your existing trigger return spring. However, for optimal pull weight reduction, a reduced-power trigger return spring (sold separately) is recommended. Factory springs may produce a heavier reset.

Do I need to fit the pinned sear?

In most cases, the pinned sear drops in. Some frames require light filing on the sear engagement surface or hammer block clearance. If the hammer does not fall freely after assembly, remove material from the sear engagement face with a fine stone. Do not modify the hammer itself.

Can I convert back to SA/DA later?

No — once installed, the Evolution IV permanently converts the revolver to DAO. The factory hammer and sear cannot be reinstalled without replacing the trigger and hammer block. Consider this a permanent modification.

All orders ship within 1 business day via USPS Priority or UPS Ground. This product carries a 30-day return window for unmodified, resalable condition. Warranty against manufacturing defects extends 12 months from date of purchase. Questions about fitment for your specific dash number?