The slug mold manufacturer says "pure lead"

I have an essentially unlimited supply of 99.1% lead, with .87% antimony and traces of other metals. This is reclaimed and smelted lead from the backstops at our club. Done at a local refiner. We have it in ingots at our club house for $1.50 a pound.

Is this "alloy" clean enough to fall under the pure lead recommendation?

Not planning on casting anything other than this one slug shape for 12 gauge shotgun shell use.

Your alloy should work fine. I'd call it pure lead; that amount of antimony is not enough to affect performance. I haven't cast slugs in years, but had good results using a harder alloy than what you're using, only because I had no pure lead at the time.

There’s also “THOR” or more commonly known as “Thunderzap”, which is an All Aluminum projectile/slug protected by a distinct white plastic sabot. Does horrific damage upon impact, but I can’t remember offhand if it’s available as a shotgun or .410-gauge round…


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99.1 % is about as pure as you are going to find any scrap lead , just about all lead used in construction has a little something in it ... It's too hard and costly to refine all the "impurities" out and some things are added to aide in the casting and rolling of sheet lead .
Call it pure and Roll with it !
Gary

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I had a Lyman slug mold for 12gauge that fit inside a shot cup. I cast WW (wheel weights) which is about 93% lead, 5% tin and 2% antimony, and quite a bit harder than pure lead! (Wheel Weight bullets get bigger as they cool!)

I don't believe the hardness is the reason they recommend pure lead. The different alloys when cooling settle into different sizes, even from the same mold! The Lyman Cast Bullet Handbook 3rd Edition) has a chart for the different as cast size ratios. (WARNING: Basic arithmetic skills are necessary to understand this chart!)

Ivan

Using the old Foster style shotgun slugs, the size/dia of the slug was kept slightly smaller than the common spec commercial shotgun bore size.
They usually fall thru the bore and will exit most all chokes without much of a problem.

Some of those slugs in combination with some very tightly choked barrels will not let the slug exit the muzzle easily. The slug is 'sized down' even a small amt.

If the payload were lead shot, then the BB's compress and pass thru w/o damaging the bbl.
The oversize (for the choke section) solid lead projectile is much less likely to easily reduce in size as the loose charge of 'shot'.
Pure lead being soft has the best chance of doing so w/o damaging a very tight choked bbl.

Custom loading & casting for your particular gun, bbl bore size and choke can easily avoid any problems.

But the mfg'rs added the warning many yrs ago when casting slugs for the old bird gun was just that. Many were to be shot down some very X-Full choked bbls.

The softer, the better, for a Lee key drive. The lead needs to shrink as it cools, to remove slug from mold.

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OP lead will be fine for slug casting. Much of the stories of slugs wiping out chokes is based on the old Pumpkin Ball, a solid ball. I have never come across a gun that a foster slug by one of major manf wouldn’t drop through. These stories are spread generation to next by armchair crowd.
Cut a few slugs out of shells and mic them. Then do the same to muzzles of shotguns. When you find one smaller dia. than slug, let me know.