Evolution IV Revolver Hammer Kit

If you’ve got a Smith & Wesson revolver that’s got a heavy, gritty double-action pull—think 12 pounds or more—this Evolution IV Hammer Kit is the part that can bring that trigger weight way down. It’s designed to turn your factory wheelgun into a Double Action Only (DAO) setup, meaning no single-action cocking, just a smooth, consistent pull every time. The kit replaces the factory MIM hammer, sear, and stirrup with pinned components similar to what you’d find in a Performance Center gun. With some careful tuning (and a good trigger scale), you can get that pull down to around 4.0 pounds. That’s light enough that you’ll want to handload your ammo to keep things safe and consistent. It’s a favorite for competition shooters who want a fast, repeatable trigger stroke without the risk of accidentally bumping the hammer back to single-action.

Compatibility

• Smith & Wesson J-frame revolvers (models 340, 342, 442, 642, 637, 638, 649, 60, etc.)
• Smith & Wesson K-frame revolvers (models 10, 13, 14, 15, 17, 18, 19, 64, 65, 66, 67, etc.)
• Smith & Wesson L-frame revolvers (models 586, 686, 619, 620, etc.)
• Smith & Wesson N-frame revolvers (models 27, 28, 29, 57, 58, 625, 629, etc.)
• Note: This kit converts your revolver to Double Action Only (DAO). If you want to retain single-action capability, this is not the right part for you.

Key Features

• Pinned sear & stirrup – Same design used on Performance Center hammers, replacing factory MIM parts for improved durability and consistency.
• DAO conversion – Eliminates the single-action notch, giving you a smooth, uninterrupted double-action stroke every time.
• Reduced trigger pull – With proper installation and tuning, you can drop from factory 12+ lbs. down to a competition-friendly 4.0 lbs.
• Includes everything you need – Hammer, sear, stirrup, and pins. You’ll need to reuse your factory trigger and rebound slide.
• Made in the USA – Fits Smith & Wesson revolvers from the 1980s onward (pre-MIM guns may require minor fitting).

Install Difficulty: 4 out of 5

This is not a drop-in part. You’ll need a good set of gunsmith screwdrivers, a small hammer and punch set, a trigger pull gauge, and some patience. The kit requires careful stoning and fitting of the sear engagement surfaces to get the pull weight down safely. If you’re not comfortable disassembling a revolver’s lockwork, we strongly recommend having a qualified gunsmith handle the install. We’ve got a detailed install video on our site that walks you through the process step by step.

Frequently Asked Questions

Will this fit my Smith & Wesson 686?

Yes, the 686 is an L-frame revolver, and this kit is compatible with all L-frame models from the 1980s onward. Just keep in mind it converts the gun to DAO only.

Do I need to replace anything else at the same time?

We recommend installing a lighter rebound spring (like a 13-14 lb. spring) to get the most out of this hammer kit. You’ll also want a good trigger pull gauge to check your work. The kit itself includes the hammer, sear, stirrup, and pins—everything else comes