Why Choose A Double Action Only Pistol?

posted on November 24, 2022

Converting a DA/SA pistol like the H&K USP to DAO typically requires the installation of proprietary parts. Having a certified armorer or qualified gunsmith do the work ensures the gun’s safety and reliability.

Call me crazy, but I like double-action-only revolvers and I am considering converting my double-action/single-action (DA/SA) semi-automatic pistols to double-action-only (DAO) triggers as well. The smooth, consistent trigger pull from first shot to last shot is about as simple as it gets, and the speed with which I can pull the trigger makes little difference in shots per second when compared with shooting a DA/SA pistol. On top of that, my accuracy is noticeably better when shooting DAO. 

I have been told that all I have to do is remove the single-action sear from my pistols to convert them to double-action-only and I am good to go. Is this true? I have a Beretta 92F, an H&K USP, a SIG Sauer P228 and a SIG Sauer P239 I want to convert. 
Jeffrey Theodore, New Britain, CT

It might surprise you to hear that I, too, am a fan of DAO, both in revolvers and semi-auto pistols for everyday carry and general use. 

With typical DA/SA revolvers, firing double action is as simple as pulling the trigger. Firing in single action requires the extra step of thumb-cocking the hammer. To make the revolver truly double action only, removing the single-action notch and the spur from the hammer ensures that a double-action stroke of the trigger is the only way to fire the gun.

Semi-automatic pistols are an entirely different story, however. While removing the sear from a semi-automatic pistol to disable the single-action function of the trigger may on the surface seem plausible, it does not address the other functions that the sear may have in its scope of responsibility.

For instance, your SIG Sauer P228 and P239 pistols have a safety notch on the hammer that interlocks with the sear when the hammer is forward and at rest, preventing the hammer from contacting the firing pin until the trigger is fully pulled. In addition, the sear in both pistols sits between the ejector on one side and the safety lever on the other, holding them in position. Without the sear keeping the ejector and the safety lever in place, it is possible for the guns to malfunction, affecting their reliability and safety. The good news is the P228 and P239 have both been offered in DAO configuration and the parts to make the conversion should still be available through SIG Sauer’s customer-service department. These parts can be easily installed by a SIG Sauer-certified armorer or a gunsmith. Consider sending the pistols back to SIG’s custom shop for the conversion—and perhaps a service package—which will ensure the guns are in tip-top shape when they are returned.

The Beretta 92F converted to DAO would equate to a 92D model, which is manufactured without an SA sear. However, the hammer and hammer spring, as well as the spacer bushing and spacer-bushing pin, are specific parts that differ from the 92F models. The 92D slide has to be factory fitted, which means that if you did want to carry through with converting your 92F, the complete pistol would have to be returned to the factory.

Heckler & Koch makes 10 variants of the USP, four of which are DAO. Each variant has its own, unique set of fire-control parts to afford the user the desired effect. H&K offers three trigger-pull weights in its standard DAO and LEM (Law Enforcement Modification), ranging from 5.5 to 11.5 pounds.

Because of the complexity of changing the USP from one variant to another, H&K recommends one of two options: Find a currently certified H&K USP armorer who can provide and install the parts, or make arrangements to send the pistol back to the factory. Depending upon your USP’s age, give thought to sending it to the factory for all the latest upgrades and new springs.

While converting your existing guns to DAO is possible, you may consider adding to your collection and keeping what you have in their present configurations. DAO police trade-ins can usually had inexpensively. Most have been carried a lot and shot little—a bargain.

Regardless, always err on the side of safety and reliability, and it will be hard to go wrong.


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