16:1 alloy hardness questions...again

If you members remember my rant from when I first started casting back in 2017 and "tried" to mix 16:1 using pewter and pure lead. My BH ended up 7.5BH. I remember buying a lee tester and testing my "pewter" which was only 7.5 BH to begin with. Obviously it had ALOT pure SN mixed in with the pewter items I used. I casted up 10mm with the rest of that alloy mix the other day and even sized 2,000th over and PC that passed the smash test I got leading. We'll today was the day!!! After that mishap I only bought and used dinnerware pewter in my 50/50 mixes and just to add 2% to help with mold fill outs.

Today I grabbed some of my current pewter ignots that I WQ and had sitting around for a few months. The BH was 21. Way different reading than my first batch of 2017 pewter.lol. I used my some of the same orignal flooring with a BH of 4.7. I mixed 8 pounds of the flooring with 8 oz of 21BH pewter. Fluxed and dropped into ignots for testing. I dropped a few ignots in cold water. Let them sit for 10min till cold and tested. It got a reading of 10.4BH with my lee tester! I did it!lol. Now my question is should I let the alloy sit a few days and check again ? With pewter you really don't know what's in it I'm guessing. I would assume a true 16:1 alloy should be around 11BH and I'm just a little softer. I want to use this in my 10mm at full bore velocities. Is it going to be hard enough? I will PC it. P.S. thanks for the help Larry. He helped me realize the first batch from 5 years ago is basically 40:1. Still works great with GCs to 2100fps and no leading in my 35 rem and 1600 fps in my 77/44 with GC devastators.

Bullets containing 2% antimony, oven heat treaded, dropped in cool water, take 2 weeks to fully harden.

Should be some in pewter, per the google search.

Thanks, saw that when I googled. Looks like modern pewter has up to 7% in it. Figured with water quenching a few samples I might have sped up the process of the air cooling samples. Guess only time will tell.

7% antimony water dropped should harden fully in 1 hour or less.

So my max is what it is …10.4BH. A true 16:1 is around a 11BH if I remember correctly? If so the magic question is how much more pewter to do need to add to bump it to 11BH? I used 8oz for 8 pounds to make my 10.4BH. It’s to early to do math in my head but I’m guessing another ounce or two?

Your pewter is probably between 88-93% tin, not pure. This means you probably added 7.2 oz of tin, .3 oz of antimony, .3 oz copper and a few trace elements. There likely isn't enough antimony to affect your alloy.

7.2 oz of tin divided by 136 oz total is 5.3% tin by weight. 16:1 alloy is 5.88% tin by weight. You are a little low on tin, that's why your hardness isn't quite up where you expect it.

If you have .3 oz antimony in 136 oz that is 0.2% antimony by weight, not enough to water harden.

So I need to add approx one ounce of the same pewter alloy I used back into my original mix and I should be pretty close, or right on, to 11BH which is what it’s seems what 16:1 alloy should be. Thanks

I’ll melt everything back down, add an ounce, pour a test ignot, water quench to cool it down quickly and test. If it’s to hard or soft I’ll add or subtract a little more to my mix I left in the pot all heated up and ready to got… and cast with it.

Just tested my WQ 16:1 vs AC. They both tested EXACTLY the same hardness of 10.4 again. The smallest piece of pewter I had was 2oz I threw it into my mix and will know shortly if it took to 11BH...stay tooned!

Tried 2 more oz and fluxed. Still at 10.4 BH. Next smallest piece of pewter ignot I had was 4oz. Added, fluxed, and tested...11BH! Took 14 oz of my 21BH pewter along with 8 pounds of 4.7 BH lead to get 11BH. Mold is warming up and ill drop a few.

Thanks for the help!!!!!