I heard tuning forks.
I am also planning on using the solventtrap.net kit to do my form 1's when the are approved. It sounds good. How did you form the plugs?
I used the torx bit method. That was the quickest and easiest.
Aluminium end caps too? I'll be keeping track of how yours hold up. I still have a nice Prepper Discount aluminium tube. Maybe I should make another one for 5.56.