I have an idea about the use of copper tubing as jacket

[tiger762]

Cut length of 1/2" copper tubing
Place lead core inside. A weight that once compressed will be a little below the case mouth
Seat the core in the tubing so that the outer diameter is 0.510" and the lead is tightly compressed and below the case mouth
Now, put the seated core/jacket in the point form die
The base will be open and the nose will be mostly formed over

This would avoid going through all the steps of folding over the tubing. Now some will say the pressure will push the lead core through the tubing but we know that's hogwash. The same pressure pushing on the lead is pushing on the edge of the tubing. Was thinking of different ways to make jackets..

[Pipefitter]

Or you could use your core seat punch to push the bullet partway into the point form die and then reverse the slug to completely form the point, giving you a bit of "fold over" at the base

[Char-Gar]

Cut length of 1/2" copper tubing
Place lead core inside. A weight that once compressed will be a little below the case mouth
Seat the core in the tubing so that the outer diameter is 0.510" and the lead is tightly compressed and below the case mouth
Now, put the seated core/jacket in the point form die
The base will be open and the nose will be mostly formed over

This would avoid going through all the steps of folding over the tubing. Now some will say the pressure will push the lead core through the tubing but we know that's hogwash. The same pressure pushing on the lead is pushing on the edge of the tubing. Was thinking of different ways to make jackets..

You are at least 50 years to late to have a novel idea. The original Barnes line of bullets used copper tubing for jackets with a dead soft lead core. These were formed much in the way you envision. These had a very good reputation as when the hit an animal they did not blow up, but balled up and kept on going.

After the company was sold by the family, the construction was changed to a more traditional form. I still have a couple of hundred 225 grain Barnes 30 caliber bullets made as above.