Alright, I did a quick trial to see what would work in regards to pimping the tube... Here's what I come up with.
The end cap (where the wooden dowel is, not the loading end):
I tried a few different cases I have access to and 44MAG seems to be the best. I tried to crimp it as much as I could to see if I can get some tension...

...almost. Not tight enough though. Still some room, but we are talking fraction of a mm. So this is a win - healthy amount of epoxy and this is going to work very well, I think.

Since I also tried a 308 case, I had the neck end ready to go... But I am not convinced that this is the way to go.


Perfect for size, but I just don't like how it looks. I think I will stay with the original plastic caps for the business end of the loading tube for now. I have another idea I want to try, sort of like a kettle spout cap - but spring loaded.