Don’t stake your fortune on my designations. I have always assumed that the T116 followed a similar line of progression as most other pre-NATO cartridges. That is, 47mm, 49mm,and 51mm cases. T116, T116E1, and T116E2. HWS III could prove me to be way off-base.
You made an interesting observation, one that I hadn’t considered. Since the “T” rifle was under development concurrently with the T65 cartridge, it may be that the long neck Grenade Cartridges were made to test in one of the prototype rifles???
Acetone isn’t that bad. I use it all the time and I still have all my - hmmm, what was the question again? It’s the primary ingredient in nail polish remover and you see ladies in the beauty salons sitting with a cigarette in their mouth while the attendant splashes it on their nails.