Derringer Design

[jdgabbard]

I've been toying around with building a derringer pistol for some time. I sat down today and started putting everything on paper. Well, rather in CAD. I have the basis for what I think is the start of a decent design. But I wanted to get some input from others who may have tacked this topic in the past. Specifically I am currently interest in comments on my trigger/hammer design.

The three pictures below show the action in it's three states, uncocked, half cocked, and full cocked. This is intended to be in the half cocked position when loading and carrying - ie, my intent is to have the trigger non-functional when half-cocked. To achieve this I have designed the notch with somewhat of a hook that should capture the sear of the trigger. Hopefully preventing the trigger's ability to release the hammer. In the full-cocked position, it should hopefully allow the release with a slight additional amount of spring pressure from the mainspring, since the angel is about 80 degrees.

The mainspring provides pressure to the hammer by means of a cam locked strut with a coil over spring resting in the grip spacer. The trigger will have a return spring to press the sear surface against the hammer surface.

Feel free to critique it. This is just the initial phase of design here....

[LAGS]

Your design looks very close to the design I will use to make a In Line cap and ball single shot pistol.
I planned to use a Coil Spring for a mainspring on a guide.

[jdgabbard]

Your design looks very close to the design I will use to make a In Line cap and ball single shot pistol.
I planned to use a Coil Spring for a mainspring on a guide.

Well, I suppose there are only so many ways to accomplish a simple hammer fired design. Good to know I'm not too far off of the method others are using. Here is a cutaway shot showing the overall layout of the frame and internals. The Breachface I'm going back and forth on. I'm not sure if I want to bolt, rivet or silver solder it in place. The rest of the gun is designed to be broken down to allow a complete disassembly. I'm thinking of using 4140 for the breach face, and mild steel for the plates. Intended chamber is up to 38spl.

[405grain]

Your design looks pretty good. The only thing I'd suggest is that you reduce the opening in the grip that's behind the hammer. If crud can find a way down into the mainspring housing and jam thing up, it will certainly try. Also, and this is just an uneducated opinion, try to make both the latching mechanism and the barrel pivot just a little beefier than you think it needs to be. Always better to be too safe.

[jdgabbard]

Your design looks pretty good. The only thing I'd suggest is that you reduce the opening in the grip that's behind the hammer. If crud can find a way down into the mainspring housing and jam thing up, it will certainly try. Also, and this is just an uneducated opinion, try to make both the latching mechanism and the barrel pivot just a little beefier than you think it needs to be. Always better to be too safe.

Well, the opening is there because I’m just not quite sure how much room I’ll need yet. Unfortunately there will have to be some open areas. Luckily, the design is loose enough it should still operate.

As for the beefing up of the design, a lot of these measurements are just something to pencil in for now. But yes, I value my face and eyes too much to not ensure it is a safe firearm.


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