Swaging LARGE diameter spheres, bullets

[Cat Whisperer]

I'm on the verge of making my own moulds for small cannon and mortars.  These would range in size from 1" to 4.5" with most being in the 1-1/2 to 2-3/4" range.

When casting LARGE objects (like 4.5" from zinc) the shrinkage becomes severe.  It opens up pockets and spheres aren't.

So if I cast a lead 1-3/4" sphere (for golf ball caliber mortars and cannon - I have both) would it be possible to swage them into more spherical condtion using, say, an hydraulic press or 16 lb hammer?

[kciH]

Cat,
The original swaged bullets where actually made with simple dies and a hammer.  Your project seems a little more ambitious, as a result of the sheer size of the projectile.  I don't doubt that you could make something, or have something made in order to swage your castings down, but they would have to be softest lead you could find.  It doesn't seem cost effective to me.

You really don't want to be casting anything with Zinc in the first place, it RAISES the surface tension of lead alloys, causing them not to fill out properly.  The other problem with zinc/lead alloys is that they have to be heated to a very high temperature to have any hope of getting good mould fill with them.  At the temperatures involved, you are heating the lead too much and it is giving off toxic vaport.

[talon]

Cat Whisperer, I was thinking about making a mold for Down Rigger weights (a 3.6" sphere...10#), and thought I'd have about a 3/4"d sprew hole with a entrence port large enough to hold enough molten metal to allow for 'feeding' that internal shrinkage into  the sphere itself. There would be no way (very high pressure requirements) to swage a raw casting of this size. Final forging( your 16# hammer) of the raw casting would be the only other option of compressing those voids. Of course, on a downrigger cannonball, a few voids here and there don't mean a thing. In a projectile they are critical.

[Cat Whisperer]

kciH -

I think I will try the swaging on the 1" to start with.  After all the number of rounds isn't going to be in the hundereds, and if the 8lb doesn't work the 16 should.  From there we'll find out the limitations of the hammers and of the dies.

re: Zinc - a very reasonable metal to cast cannon balls.  It has almost the same density as cast iron.  Agree it doesn't mix with lead, but it's much easier than CI.

talon - I do like the idea of a large long sprue - for both feed and velocity of metal.