Anybody Tried This?

[Jeff82]

I've noticed that the BHN of my bullets is effected by ambient temperature (casting in the winter and air drying versus summer). In warmer weather I was thinking of dropping the bullets in a tin tray, and having the tin tray surrounded by water. I think this would be half-way between water dropping and air drying, and that it might mitigate the effect of air drying in different temperatures.

Any thoughts?

[RickinTN]

I have gone to heat treating for much the same reasons you're mentioning. My thought are this. With water dropping you can have the inconsistency of the time it takes to drop the bullets into the water and the bullets must be sized after the water drop, which I understand work-softens the bullets. With heat treating the sizing can be done before the heat treatment and later lubed in an oversize lube die. This way there is no work softening of the bullet and they are all the same temperature when they are submerged in the water. I bought my heat treat toaster oven at the local Goodwill store for $10 and use my alloy thermometer to check my oven temperature.
Good Luck,
Rick

[Jeff82]

RickTN,

Interesting. I've never tried heat treating. The reason I don't purely water drop is that I'm trying to keep the BHN low 9-10 range. Could you explain how you heat treat and the extent that is increases BHN?

Thanks.

[RickinTN]

Jeff,
I got most of my information from the LASC sight (Linked at the bottom of any page on this forum). You can vary the obtained BHN of heat treated bullets based of course on the original alloy and the time/temperature treated. If my memory serves me correctly clip-on wheel weight alloy can be treated for a hardness from about 18 and on up depending on oven temp. The information on the LASC page is interesting, and probably enough to keep you busy studying for days. If your hardness goal is in the 9 to 10 range I'm thinking heat treating is not for you. I'm curious....How much variation in hardness are you realizing due to differences in ambient temperatures?
Rick

[cbrick]

You could also use the oven to anneal your boolits, this way they will all be the same regardless of when you cast them. Place your boolits on a tray & put into oven set at about 275-300 & leave them in there for an hour, after the hour just leave the boolits in the oven and turn it off letting the oven and boolits cool to room temp. They will all be the same (assuming all the same alloy), then don't check the BHN for several days.

I'm curious also how much of a difference there is casting from Wisconsin winter to summer. What determines the final BHN is how fast they cool and if your casting outside in Wisconsin in the winter (your a better man than me) they would cool much faster so . . .

Rick

[runfiverun]

I have air quenched boolits in the cold.
the quenching comes from the rapid cooling of the boolits surface not the water it's dumped in.

I keep my shop a pretty consistent 55-65-f all year around, and also try to keep a humidity in there.
not so easy to do here.

[Jeff82]

If an average Wisconsin winter temperature is about 20 degrees and an average Wisconsin summer temperature is about 80 degrees, I'd expect a variation of about 2 BHN with an alloy of 1.0% Sb and 1.0% Sn between summer and winter casting. This would be a difference of between about 10 bhn in the winter and 8 bhn in the summer.

Another complicating factor for me is that in order to air cool a bullet to achieve about 9 to 10 bhn, I need an alloy that contains only about 1.0% sb and 1.0% sn. A difference on as little as 0.1% will produce a noticable difference in Bhn.

I'm shooting 357s. These bhn differences seem to make no difference in pistol accuracy out to 50 yards. When shooting a carbine at 100 yards small differences in bhn measurably affect the point of impact and accuracy. I routinely need to adjust me sights for differences in bhn at these ranges.

Annealing would be another possible solution. Does it increase bhn?

[btroj]

Annealing, like Rick mentioned, will not harden the bullets. What it will do is make them uniform in hardness and the temp at time of casting will no longer be relevant. As long as you use a consistant alloy the hardness will be determined only by the temp you set on the oven.
Age can play a role too as many alloys change in hardness over time but if you cast them, anneal them, and let em sit for a few months they will all even out.

[sqlbullet]

Your best option would be to heat the bullets to 350° for one hour and allow them to cool in the oven. This will ensure a uniform cooling environment and would provide you with the most consistent BHN year round. However, this bhn may be softer than you want with an alloy of only 1% Sb and 1% Sn.

My tests with an alloy of 3% Sb 1% Sn gave a hardness just shy of 10 in two out of three batches. Results here (http://fellingfamily.net/isolead/), scroll to the bottom and look at series 3, 9 and 15.

Despite the common wisdom here that oven heat treating is more consistent than quenching, the extreme spreads and std deviations of series that were oven treated were not statistically different from those quenched from the mold. These were cast to a uniform cadence by counting aloud between cast, cutting the sprue and dropping the bullets from the mold.

I have also not found a measurable difference in hardness of bullets that were quenched and sized versus just quenched. Yes, lead work softens, but unless you are sizing down quite a bit, the lead just isn't worked beyond a thousandth or so deep. The rifling will engrave 4 or five thousandths, or 400-500% deeper than the lead worked.

I know there are many who vehemently disagree with these last two findings. In their experience I am sure they have found results they are happy with casting, then sizing then oven treating. My tests and my shooting don't justify the expenditure of time for my guns.

[Jeff82]

Thanks for the replies and hardness study results. Seems like treating with low heat (350-degrees) and slow cooling reverses the effects of water dropping or ambient weather cooling. I think the result of annealing for me would be similar to the BHNs that I get from air cooling in the summer months. I'm guessing that a 1.5% sb / 1.5% sn alloy would put me near 9 bhn when annealed.

Do I understand this correctly?

Thanks.