Bullet Bhn changes......

[Harry O]

I have an equation I use for figuring out Bhn and it has worked well in the past. I generally use a mixture of pure lead, monotype, and pure tin to get whatever I want in Bhn. The bullets are air dropped into a towel. The equation gave pretty good results up until now.

Recently I bought some "lead" that was reportedly from truck wheelweights. I did not see them before they were melted down and cast into approx 4" x 24" x 1/2" ingots. They were Bhn 16-18 when I got them. I broke one up and melted it down to cast it into 1lb ingots. The ingots were Bhn 9 after I recast it.

I used those ingots (along with a little monotype and a little tin) when I cast up a bunch of bullets for the .30cal carbine. I was trying for Bhn 15 with a gascheck for these bulllets since I planned to load them up to full pressure. When I got done casting them, they tested at Bhn 15-16. A week later, they tested at Bhn 18-19. No problem. I just retested them (a month & a half after casting) and they test out at approx Bhn 20-21. I do not have that happen with the bullets from melts I made starting with pure lead.

I am thinking that the WW ingots I recently bought have a lot of arsenic in them? They were not water dropped. Does that mean that hardening can take place without quenching them? I doubt that this is a problem, but I will be trying some this weekend to check for accuracy.

[sagacious]

...
I am thinking that the WW ingots I recently bought have a lot of arsenic in them?
...
That was my guess even before I got to your supposition quoted above. To my knowledge, it doesn't take a lot of arsenic to effect a noticeable change in hardness, so even a little will do it. Your pure lead/monotype/pure tin would ostensibly contain no arsenic, so that seems like the most likely suspect.

Yes, in my experience, bullets cast from ww's will gain in hardness over time. If you want them all the same, you'll have to 'season' them for a month or more before shooting them. That may or may not make a difference in your application-- only testing will tell. Good luck.

[RobS]

I've have found that casting when it is really cold can make a difference regarding the BHN of a bullet. Casting in the summer heat of 100 degrees in my garage I will end up with around 11-12 BHN for WW bullets and then in the winter when the temps are in the 20's in my garage I end up with a bullet at 17-18 BHN. It was from the same batch of lead so that part of the equation was constant.

I discovered this quite a while back as I was loading up some mid loads for the 45 colt in the winter and had the same powder charge I used in the summer with great results. The winter bullets I ended up at the range with tons of leading in the barrel. I initially thought that I made a mistake on the powder charge or because of the ambient temperatures the powder was yielding higher pressures. Testing at home proved that it was not the powder charge and I just couldn't see having the temperature change on the powder being that big of an issue so I tested the bullet hardness and found the culprit.

Air cooled, water quenched, heat treated doesn't matter as WW bullet hardness changes. I've had a lengthy discussion about heat treating on this forum just recently and while you can heat treat to make a bullet hard you can also heat treat without quenching in water to bring the BHN back down as well. This is what I did with my WW aircooled bullets that were reading higher than "normal" BHN.

When you made up your ingots they are much larger in shape than the bullets you casted so their cooling time is less effected as it takes them longer to cool down. So for all my "hard" bullets, I took them down stairs into my man cave and put them in an oven at around 450 degrees for an hour. After an hour I shut off the oven and left them in the oven to let them cool down slowly and low and behold there you go..............11-12 BHN.

[John Boy]

Harry, here is a chart that was prepared by Dan Theodore, a CA gun crank that you may find interesting ...

http://i222.photobucket.com/albums/dd220/Meadowmucker/Bullets/CCF121996_00000.jpg

The alloy ratios are in the box at the top right of the chart. The composition of clip on WW's is: 2.96% Sb, 0.41% Sn, 0.174% As, balance lead

[Harry O]

My casting room is in the basement (with a fan to push air outside thru a basement window). Temperature does not change a whole lot from winter to summer.

However, I do know the size of the bullet does make a difference. The equation I use to predict the Bhn was made with 200gr bullets. If I cast 100gr bullets, they are approx 1 Bhn harder (more) than it would be with 200gr bullets. If I cast 400gr bullets, they are approx 1 Bhn softer (less) than it would be with 200gr bullets. I take that is happening because of the difference in cooling time.

I used to have some car wheelweights. I know they were car wheelweights because I melted them down and removed the steel clips myself. I used them up when I wanted something harder that using pure lead. It is all gone now. However, the bullets I cast with that stuff never continued to harden like these. There is something different in this batch. Whenever I need some hard bullets in the future, I know what to start with.

[RobS]

Without the temperatures effecting your casting then it is most certainly the alloy you have. I too have noted the same regarding the differences in weight of bullets and their BHN readings. Either more antimony or arsenic or more of a combination of both looks to be what is creating the harder bullets for you. Like you said you have a harder alloy to use when needed.

Regards,

Rob