So far I've only made and fitted one pistol butt cap. I have not been able to find much information on this subject. This "tutorial" describes how I did it. I'm hoping the more experienced builders will add tips and comments.
1.Making the butt cap pattern.I checked my last practice pistol stock with a pattern gauge and found it wasn't completely symmetrical. So my first step was to make a better pattern for the butt cap area. I used a pattern gauge to make sure it was completely symmetrical in both the horizontal and vertical planes.
2a.Making a lead swag block.I tried using the pattern to cast a lead swag block. The lead I used came from wheel weights and proved to soft for swaging 0.08” thick brass. Even though I had annealed the brass at 1472 ° Fahrenheit for 20 minutes, the cavity deformed. Is there available a harder, low temperature casting alloy?
2b.Making a wooden swag block.I inlet my butt cap pattern into a block of hardwood, using inletting black. This worked with 0.08" brass.
3. Making a pattern for the brass.Use a piece of paper to measure the length of the butt cap pattern, from the tip of the cap to the end of the tang. Now measure across the pattern at ½" increments.
Mark these measurements off on a piece of paper and draw a tear drop. This is a rough pattern and has to be adjusted. To adjust the pattern, glue it to a piece of 0.04" brass and cut it out. Take a knife and score the horizontal and vertical lines in the brass before annealing it.
Carefully beat the brass down into the swag block. Anneal often. You will now find out that your pattern is too big and the brass sticks way above the swag block. But the brass is still the same thickness (0.04”).
The circumference of the cup area of the pattern is larger than the circumference of the cavity in the swag block. When the metal gets pushed down into the cavity, the edge contracts and extra brass (marked red) gets pushed out of the swag block.
Check the lines you score in the brass. Measure how far they stick above the swag block and use these measurements to adjust your pattern. I had to reduce my pattern with about 1/8" to 2/8" around the whole cup area. Test your adjusted pattern on 0.04" brass. Working with 0.04" brass is a lot easier and quicker than using 0.08"”brass. Try to make your pattern as small as possible and still fill the swag block. The less metal you use, the less metal you have to move , the easier it will be to fill the swag cavity. When you are satisfied, glue the pattern on 0.08 brass and cut it out.
4. Swaging the butt cap.Take your time. Don't hit the metal to hard, or you will stretch and thin it. Anneal often. 0.08" brass work hardens quickly. I had to anneal the brass 12 times to get it all the way down into the swag block. This is how it looked after the first round of swaging.
Notice there is a small“crease where the tang meets the cup. This has to be"ironed" out as soon as possible. If you ignore it, it will keep getting bigger , the brass will hang up on it and not go down into the swag block. Use a big punch as an anvil and hammer out the crease. This will also start the tang bending up.
Use as big as possible punch to drive the brass down into the swag block. This will give a smooth even surface on the butt cap. If you only use a small punch or a ball point hammer, you'll get a bumpy, warty surface that will need a lot of filing.
5. Filing the edges of the butt cap.Drill the screw hole in the butt cap and mount it in the swag block.
File off the edge of the brass cup that sticks above the swage block and file a draft on the tang.
The butt cap is now finished, ready to install on the pistol.
Best regards
Rolfkt
