Copper tube jacket questions

[BT Sniper]

Hey guys,

Going to try making riffle bullets with jackets made from copper tubing someday. Did some searching on the sight and it seems the jacket is always "drawn" or sized down to proper size. My question is could the tubing be swaged up in size instead? For example .257 or .264 from 1/4" (.250) tubing or .338 from 5/16" (.3125)? This would seem to eliminate a step in the process. I can only think the reason for drawing the tubing is that it helps with uniform wall thickness and of course proper size, is this the case? Is the wall thickness of standard copper tubing uneven to begin with?

Anyone have some experience or addvise that would care to chime in. I'll be making my own dies for the jacket making process as well. Of course this is a whole nother learning experience for me.

Thanks

Brian

[phil218b]

Brian
The wall thickness of copper tubing is the main factor, commercial jackets are tapered and thinner than the copper tubing. It would take a lot of pressure to swage up a tubing jacket and a big press and die, the core swage rod would have to fit exremely tight not to allow lead seeping and lose pressure and weight. In a m type die you would more than likley belly the die from pressure.

[BT Sniper]

Thanks Phil,

I didn't think about the extra thickness of the copper tube. I'm sure you are correct about the extra pressure needed. If I shot a 25 I may be tempted to try the bump to .257 from .250 but I supose .264 would be a bit much.

[Red River Rick]

BT Sniper:

When you say "Copper Tubing", are you refering to the "Soft Coil" or the "Hard Rigid".

The "Soft" coil tubing doesn't work very well, it's too soft to support itself when forming. The "Hard" rigid tubing in straight lengths is more preferred and will provide better results.

Using 5/16" tubing and having to reduce the diameter will work better rather than trying to bump the jacket up. It will require a few additional draws to get the jacket to the size you need, but it does work.

Hard Copper tubing also comes in various wall thicknesses, the thinner the wall, the easier it is to form. And will probably exert less internal pressure on your dies.

FWIW

RRR

[Linstrum]

I have "drawn" copper tubing up in diameter no problem when I needed oddball diameters of tubing that were closer to a smaller size tubing than the next larger size up. The way I did it was by pulling a mandrel through the tubing, the mandrel was attached to a long rod inserted all the way through the tubing. I pulled the rod and mandrel through the tubing two ways, one was with a regular cable come-along like for lifting engines, and the other was with my tractor. The tractor was of course tremendous overkill, but I prefered it to the come-along because the tractor supplied one long, smooth continuous pull while the come-along pulled stop-and-go since the lever had to be operated back and forth. The stop-and-go pulling makes very slight differences in the finished diameter, which probably would not cause trouble and if I didn't have my tractor available I'd probably just use the come-along.

For epanding the diameter of 1/4-inch inside diameter tubing, I made the mandrel by adding weldment to the head of a regular 1/4-inch grade-5 hex bolt and then machined it so it was a round knob with a 45° included-angle lead-in taper on the leading edge. Getting the mandrel started was a real headache problem because the tubing had to be expanded to get the mandrel started inside the tubing. I finally had the idea to split about the first 2 inches of one end of the tubing to give me something to clamp onto the tubing by to take the tension while pulling the mandrel through it. The mandrel going down the inside of the tubing looked like a snake eating a rat as I pulled it through. To do a long length of tubing I had to bore about a 1/2-inch deep by 3/16-inch diameter hole in the end of the mandrel and then silver solder a 10-foot long by 3/16-inch diameter single strand wire into it. I used some 3/16-inch chain link fence top support wire, which is plenty strong to take the tension. I also had to fine-tune the diameter of the mandrel to get the outside diameter of the tubing I wanted since the tubing wall thickness stretched a bit. I eventually made the mandrel a bit oversize and then drew the expanded tubing back down a few 1/1000-inch to get a good uniform diameter. When I was finally set up it didn't take too long to expand the diameter of the tubing, but for sure if I only needed a short length of tubing I would just take oversize tubing and draw it down instead of going through what I did. If you need a lot of tubing only then is it worth expanding it up in diameter.

I used regular Vise-Grip pliers to grab onto the tubing and pull rod, and Ivory Soap paste to lube the inside of the tubing. Ivory Soap paste works great for drawing copper and most other metals, just grate some with a cheese grater, stir in a tiny bit of water, and then let sit awhile to soften up into a paste.


rl543