How big a size diff. to expect from different alloys?

[patrick_sween]

I am using a Lee 314-90TL SWC, and out of pure COWW I got an as cast diameter of 0.3150 to 0.3155. Just tried a few out of pure SOWW, which I understand should be pretty close to pure lead, and as cast they measure 0.313. I know different alloys will cast to different diameters, but is this about right for direction and magnitude? I'm very new to casting and this is my first and only mould to date. Thanks!

Patrick

[454PB]

In my experience, that seems a bit much. It could be that the SOWW are not filling the mould as completely as the COWW because of a total lack of tin.

As an example, a mould that casts a .430" slug in COWW will usually cast around .432" in linotype. Smaller calibers will produce less differential.

[tazman]

That is the correct direction. Not certain of the size as there are several variables that can effect that.
Pot temperature, mold temperature, and the specific alloy all have a direct effect on the as cast size of cast boolits.
As a rule, the harder the alloy(more tin and antimony) the larger the as cast size will be. Linotype will give you nearly the largest as cast size from your mold. Pure soft lead the smallest.
The temperature of your mold has a large effect on the as cast size.
The temperature of the pot has a direct effect on mold temperature and boolit size.
I try to get molds to drop a bit larger than what I want to shoot so I can resize them to a consistent diameter.
Often molds drop boolits that are slightly out of round. I use the sizer to true them up.

[patrick_sween]

Thanks, that's kind of what I figured, and I know I need to add some tin as I wasn't getting great fill-out. I'd like to keep them soft, so I'll probably just add 1-2% tin and see where I am. I am also not against lapping out a thousandth or so if I have to, but would like to get them coming out at .314 without lapping if possible. Thanks again.

Patrick

[prs]

Lee claims their nominal size will cast from as stated to .003+ with 95Pb:5Sn. Pure lead will cast a "little" smaller because that is just how lead does and also because you will tend to cast with hotter mold when attempting pure lead. Tin and antimony tend to allow lead casting alloy to shrink less with cooling and do not need as much mold heat to cast accurately; both factors gain you size. But, crank up the heat to get very frosty lead/tin/antimony boolits and they will drop relatively smaller too.

prs

[Yodogsandman]

Patrick, try this link, it should answer your question...

http://www.lasc.us/CastBulletNotes.htm

[243winxb]

Bullet Sizes & Weights – How to Vary Them http://www.redding-reloading.com/online-catalog/88-bullet-moulds-charts