[Kermit]

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!

 

[unclenick]

I don't believe you'll find a single answer. Elmer Keith used 20:1 and 16:1 lead:tin to develop the .44 Magnum. If the revolver's chambers are smooth and uniform and the bore is smooth and free of constrictions and is either uniform or tapers to a slightly tighter muzzle (half a thousandth to a thousandth tighter), but never the reverse, you will find it will shoot well with softer lead than guns not in such good condition for lead bullets.

Firelapping will produce smoothness. If the chambers are not perfectly uniform, you can get them reamed. You can have it done for a little under $40 here.

I find most revolvers and lever guns, especially as the alloy gets harder relative to the pressure of the load, will shoot a little better with bullets about 0.002" over groove diameter rather than the standard 0.001" over normally used for lead. Casting your own will let you experiment with that. The wider diameter removes some of the reliance on pressure to upset the bullet to obturate the bore, hence you can use greater hardness than your load can upset when using 0.001" over groove bullets.

Read the sticky on bullet hardness at the top of this forum. It will take your through some of the considerations. I also discovered I have an old Excel file for estimating minimum and maximum B.H.N. I don't even recall where I found the formulae? I'll have to review it. If I think it is reasonably reliable, I'll attach it or make it available for download. In the mean time, it needs your barrel length (I assume this is a revolver) to make the estimates, if you could post that? With the estimates, you can look up an alloy in the Lyman book or some other source of BHN v. alloy numbers. The LASC site has some, I believe? I'm sure the Cast Bullet Association forum does.

If in doubt, I would default to the standard Teracorp magnum alloy mix and experiment from there. That is 6% antimony and 2% tin and the difference being lead, IIRC, and the BHN is around 16? That should do fine in the range you are loading in, provided the bore isn't too rough.

 

[Kermit]

Uncle Nick,

I'm shooting a Ruger New Model Blackhawk with a 6 1/2" barrel if that helps. Thanks.

 

[unclenick]

With that barrel the estimator says minimum BHN's would be 7.5 and 14 for the slower and faster loads. Maximums are around 16 to 25. I think you're just going to end up with the BHN 16 bullet as I suggested earlier. So, no, in the end it didn't make much difference to the earlier guess. The 92%:6%:2% lead:antimony:tin mix will probably serve both loads.

 

[RML9MM]

unclenick, I have wheel weights, pure lead, and pure tin. What ratio would give about a 16 BHN ?

 

[unclenick]

There's no simple formula for hardness from different mixes, AFAIK. Wheel weights don't have as much antimony as the Terracorp mix, and tin doesn't increase hardness as much as antimony, so an exact mix would have to be determined experimentally. Also, wheel weight metal varies in composition regionally as well as the formula having been altered over the last 20 years in general, so it isn't the constant starting point it once was. It looks to me like adding 6% tin by weight to the wheel weights will get you a good start. If you have a means of measuring hardness, you can try increasing that. It might need as much as 10% tin addition or so.

You can also water quench wheel weights to harden them further, but you need to get a good consistent procedure for that. You will need a means of measuring hardness, too, if you are going that route. I usually add 2% tin to wheel weights so they cast a little more easily, but it isn't required. That amount of tin won't adversely affect water quenching. Getting more tin than antimony, though, will make quenched bullets age-soften more rapidly.