I made these punches thinking they'd save time over making something more along the lines of a top and bottom swage. If I thought I'd be making a lot of these trade gun pipes I'd have gone the extra mile, but really this works quite well.
I cleaned off the end of a a square bar of mild steel, layed out a pattern and chiseled / filed in the ridges and furrows.
From there I struck the punch with a hammer into a chunk of lead to create an impression, then set annealed pieces of sheet brass over the impression and drove the punch into the brass.
To save time making tools and get back to more exciting gun work, the punch was made half the length of the pipes. To make the full length pattern I reverse it and hammer again.
Here's one quickly rolled around an unsuspecting drill bit and pinched in the vise to create the tab.
I have made a couple others with different patterns.