Another alloy mixture question

[Kermit2]

I'm new at this and just getting into boolit casting so forgive my ignorance, and please be patient with me. I'm preparing to start casting my own boolits for the .41 magnum. I'll be using RCBS mould #41-210. This mould appears to produce flat based boolits which is a must in my book. I've been using flat based cast LSWC 215 grain boolits so far, but want to start making my own. I'm using 7.2 grains of Universal powder for my everyday load and averaging 1050 fps, and have shot the same boolit with up to 19.2 grains of 2400 (1400 fps) with no problems in my revolver.

I'd appreciate information as to what is the correct alloy mixture for casting .41 magnum boolits. All information as to what mixture I should use for casting boolits for this purpose would be appreciated. Thank you!

[grumpy one]

What works in someone else's revolver is not necessarily what will work in your revolver. For low pressure loads there are advantages in keeping the bullets fairly soft, but there are limits to this when you get into magnum pressures. Also, the relationship between the diameter of the front of each cylinder chamber and the barrel's bore is critical, and bullet hardness is one of the parameters you juggle when it is necessary to compensate for something not ideal in the gun's dimensions.

Having said all that, since you want to go up to quite high pressures, you probably need something harder than air-cooled wheelweights (about 10-12 BHN). A number of magnum revolver users find that about 18 BHN works best for them - so you may find it worthwhile to at least try this hardness level. You have not said whether you are going to hunt with these bullets or just use them for target shooting, and this makes a difference to how you should approach getting the right hardness level. For target shooting, you just want the right hardness - other properties such as toughness probably don't matter. For hunting, toughness is likely to be of primary importance.

The cheapest way to produce 18 BHN bullets is to heat treat pure wheelweight alloy. If you are lucky with your mould and very skillful with your casting technique you may get this consistently just by water-dropping your bullets when you cast them, but more likely you would get inconsistent hardnesses that way. Oven heat-treating is the most reliable way.

If you want to make your bullets easier to cast, add about one percent tin to your wheelweights. If you want to make them both miraculously easy to cast and extremely tough, add three percent tin. In either case, you will still need to heat treat them to get 18 BHN.

My preferred way to make target-shooting bullets easily and cheaply, is to mix 25% stick-on wheelweights with 75% clip-on wheelweights. Because most stick-ons have over 1% tin, the outcome is around 0.7% tin and between 2 and 3% antimony. This alloy is cheap, casts and heat-treats well, and has a reasonable level of toughness - especially compared with hard-cast alloys such as 2% tin, 6% antimony, which have poor toughness.