I finally completed my MagLite fire piston last night after fiddling with it off and on for several days. The original intent was to make a fire piston that could be easily replicated by someone with basic handyman skills, with inexpensive parts that are widely available, and with tools that most people have or can obtain on the cheap.
I started out using a galvanized pipe, but that was a complete failure. The inside of the pipe was way too rough, and I am way too lazy to smooth it out. The next attempt was with a copper pipe, which did work fairly well, but I could not think of an easy way to have a removable cap made with common tools. So I sat there thinking about what I could possibly own that had a tube with a smooth interior and a removable cap on the end. I know, in hindsight, it is awfully obvious.
I used a MagLite because many people already own at least one, and it is completely worthless to me. I haven’t touched my MagLites since I bought my first Fenix flashlight a few years back, except to use a couple of 2D bodies to make some obnoxiously bright lights. I started trying to get a fire piston working using a 2AA MagLite body. The first attempt worked pretty well, but I could not get a proper seal for the life of me with an o-ring. I tried all kinds of sealants and epoxies on the piston and around the o-ring with zero luck. Then I wandered around Ace Hardware for a while and came across a plumbing part that looked just right, and it worked perfectly.
The final result is a MagLite that you can start a fire with with no lasers or other electronics involved. Is it practical? Hell no. You can take ten more effective fire starting tools in the space that this would take up in a tool kit. Is it fun? Hell yes. Starting a fire quickly and easily with a few simple parts is pretty cool (hot?).