Originally Posted by
captain-03
I have been reading a few post regarding heat treating cast bullets ... seems like it is something I would like to try in order to push some rifle bullets a little faster .. Got several questions about the process ....
1) What is the best method to actually perform the heat treatment .. temps, lenght of time in over, temp of water they are placed in, etc, etc ...
Probably like most people, I use the oven temperature as the way I control how hard I make the bullets. Always leave the bullets in a preheated oven for one hour before quenching. If you want to raise the hardness of straight WW, which is about 10.5 BHN air cooled, to 16.5 BHN, an oven temperature of 185* Celsius should do it (hardness always measured 14 days after HT). That is using tapwater at room temperature, but you need to get the basket of bullets from the oven into the water within say 1 second.
2) What can I expect to gain in harness from heat treatment using straight wheel weights or 50/50 WW to Pb?
WW don't have a standard composition. If you have say about 0.7% Sn and 2.5% Sb (i.e. a mixture of clip-on and stick-on WWs), and you do a maximum quench (i.e. oven temperature 240* Celsius - any more and the bullets slump in the oven) you'll probably get 24.5 BHN. If you use about 1.5% Sn, 4% Sb you'll probably get about 32.5 BHN. The hardness achieved falls off fairly slowly on the lower-Sb side: 2% Sb should give you about 23.5 BHN. I haven't tried lower Sb content than that.
3) I have read that once you heat treat and then resize, the bullet looses some of its gained hardness - true? Do you size then heat treat?
Yes, after the bullet has hardened (i.e. hours to days after quenching) if you cause the metal to yield, most of the hardening will be lost. Most people size before heat treating, but those who water drop direct from the mould size within say 2 hours of casting, and still get quite a bit of hardening.
4) How about gascheck bullets, do you go ahead and check them prior to heat treatment?
You could, in fact it's recommended, but it gets pretty annoying if you change your mind about the alloy or HT afterward since you'd be wasting expensive GCs. There are a few tricks sometimes done to delay GCing the bullets, such as sizing without GCing, then GCing later when lubing, in a sizing die .001" oversize. I'm not really sure whether this gives the same accuracy as GCing before sizing.
5) When do you lube? Soon after treatment, or do you wait until you get ready to load 'em? (I use an RBCS lube/sizer)
Depends on your lube and storage process. I don't like the idea of letting the lube dry out before shooting the bullets, so I'd rather leave the lubing (using a .001" oversize sizing die) and cartridge loading until just before shooting them.
6) How long can I store the treated bullets before they begin to soften?
The hardness increases and decreases simultaneously due to different metallurgical processes. Peak hardness is likely to occur a few weeks after HT, but the bullets will still be a lot harder than air cooled after a year.
7) Any advantage in heat treating pistol bullets (9mm, 40S&W, 45ACP)?
I'd better leave that one for people who shoot those calibers. It may depend on the particular pistol. Hardening isn't necessary for any of those, but whether some barrels turn out to like hard bullets is another question.
I know that I have asked a lot of questions, but I know that there are some of you who have ALL the answers!! Thanks!!
Reply With Quote
