Yes, another underhammer flint-pistol maker!

Well, it seems that there are now at least two underhammer builders who were intrigued enough by the concept of an underhammer flintlock to build one. Our friend Scott Coy has now joined the ranks of that elite little group who have successfully made an underhammer flintlock.

Here's Scott's story .

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My First Underhammer Flintlock

by Scott Coy

It all started as a joke!

A shooting buddy of mine stopped into my shop one afternoon to see what I had been up to. Having just finished an underhammer percussion rifle I handed it to him and asked him what he thought of it. Knowing that I am an avid flintlock shooter he said “why didn’t you make it a flintlock?” We laughed about it but after he left I was wondering if it could be done? I searched the net trying to find any information on underhammer flintlocks and found very little. Now it became a challenge.

I had been working on this underhammer rifle for nearly a month so I understood the concept pretty well. With close examination I realized that I could modify the percussion hammer to hold a flint and build a pan to hold the frizzen and I would have an underhammer flintlock. It sounded logical to me but I don’t think that it would have looked very good. A flintlock has to have a graceful S-shaped cock. To me looks are almost as important as function!

I started to draw out some ideas on paper but things didn’t progress. A couple weeks went by until one day while working on a large Siler flintlock the light went ON in my head!. I took the Siler apart and arranged the parts upside-down and at that moment I knew that I could make this thing work.

Having built several conventional flintlocks in the past I decided to use existing parts where I could. The H&A type mainspring-trigger guard was the logical choice for the main spring. I added a piece to the cut-out side of a large Siler cock, adapting it to utilize the H&A spring. This piece also has the half and full cock notches cut into it.

It’s a tricky process to get those in the correct place! I used a sear to engage the half and full cock notches and I made the trigger from scratch.

Getting everything in the proper position and working correctly took a lot of time. It was all trial and error. Mistakes were made and some parts were turned into junk, but that’s what happens when you are trying to create something new. Making something simple is a lot harder than one might think!

With my hand-made or modified parts assembled into the action I still was not sure that this thing would actually work. The main spring seemed to have plenty of power. The half and full cock notches seemed to hold, but would this thing really work? I put a piece of wood in the jaws of the cock then pulled the cock to the full-cock position. Touched the trigger and it actually worked - the first time! With the wood replaced with a new flint I brought the gun to full-cock and touched the trigger again. The frizzen gave off a beautiful shower of sparks right into the pan. I thought I had this thing whipped.

At the shooting range things didn’t go that good. It seemed that I had overlooked one minor obstacle - GRAVITY. With a conventional flinter you try to get the flint to strike about 1/3 the height of the frizzen from the top. With the underhammer design, the powder was igniting too far below the vent and ignition was very slow. I also had several flash-in-the-pans without the barrel firing. To remedy this situation I adjusted the flint to strike the frizzen at about the half-way point. I also opened the vent a bit larger than I normally would. Doing this and a few other small "tweaks" got it to fire pretty fast and eliminated those flash-in-the-pan misfires. However, I still haven’t got it to fire as fast as a well tuned conventional flintlock!

For those of you contemplating a project like this I will tell you that this is a very complicated build. The placement of parts is very critical and there isn’t much room for error. Study the parts placement and geometry of a conventional flintlock. They have been around for hundreds of years and are about as close to perfect as they can get.



For me, designing this gun and getting it to shoot while keeping it as simple as possible was the challenge. I know there are a lot of you who can do a much better job on something like this than I did and I would like to see examples of your work.


Thanks, again Scott for sharing your story.
Anyone else up to the challenge?

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