Finding a way to get hard PC'd boolits from regular COWW alloy

BHuij

Active Member
I'm trying to get the strongest COWW alloy bullets I can come up with. I understand that heat treating at close to slump temperatures and then water quenching can get COWW up to the 30 BHN range.

Trouble is, I'm powder coating in place of lube. 400 F for 20 minutes more or less undoes all the HT/Q benefits.

I've read several topics here and elsewhere, and some people were doing tests to find a way around this problem, but I never saw definitive results. So I figured I'd ask before I go through the trouble of doing the tests... although I may just do the tests anyway, because who knows if my COWW is the same as anyone else's. What I want to try:

1) Cast some bullets. The ones I'm using where hardness particularly concerns me are my .223 55 grain Lee ones, as they're intended for my AR, and I'm trying to push the envelope on velocity without losing accuracy. Water quench some from the mold and air drop others. Measure hardness immediately, and at 7 and 14 days.
2) Shake & bake the bullets at 450 F for 60 minutes, water quench immediately out of the oven in ice cold water. Measure hardness right away and at 7 and 14 days. See if PC'd bullets can still pass a smash test, or if the coating is ruined by the over-baking.
3) Shake & bake the bullets at 400 F for 20 minutes per my normal PC procedure. Allow to cool completely, then attempt a heat treat/quench at 450F for 60 minutes after the PC already cured and cooled. Measure hardness right away and at 7 and 14 days. See if PC'd bullets can still pass a smash test, or if the coating is ruined by the second baking.
4) HT/Q some bare lead bullets. Shake & bake at a temperature too low to anneal significantly (recommendations here? Thinking maybe 250 F), and see if I can get a good cure on the PC. Measure hardness right away and at 7 and 14 days. See if PC'd bullets can pass a smash test.

Ideally I'll be able to come up with a .223 bullet from my COWW alloy that remains at or near 30 BHN and has a satisfactory powder coat.
 

Will

Well-Known Member
Most of the info I have seen recently is on YouTube. Guys are using Eastwood powders and baking at lower temps to avoid losing hardness gained through water quenching.

Or you could always add antimony/copper to your alloy to give you the hardness you desire without the need for water quenching/ heat treating.
 

JWFilips

Well-Known Member
After reading your post I think it answered one of the questions I had about bullet hardness when PC'ing! Yes the baking would put the alloy back to it's original air cooled hardness.
Will has the answer You you don't mid the expense You could cast from straight Lino but for 30 BHN ( I'm maybe thinking Monotype or Foundry type would be closer)
Those would be expensive bullets however
 

freebullet

Well-Known Member
I wouldn't heat twice. Do the cook & ht in one step. The powder will turn darker due to the extended cook time, but should perform as normal. 400 @1hr should be adequate. Most of the coatings are good to 5-550 ish.
 

Ian

Well-Known Member
These are .22 bullets, it doesn't take an hour to heat treat them. I'd go in the oven at 400 for 15 minutes, which should give 10 minutes at part metal temperature, then bump the temperature dial up to 450 for another 15-20 minutes, and quench IMMEDIATELY in room temperature coolant. Make sure your arrangement will allow an instant quench, like no more than a three count from opening the oven to bullets in water. Testing will reveal how much time is needed for the hardness, but I'd definitely want to have all the flow and cross-linking happening in the correct time/temp window before working on heating the alloy to desired treatment temperature.

Use a 50/50 HD truck anti-freeze/water mix for quenching. The HD coolant has organic nitrates in it which resist cavitation from steam bubbles. It's also less expensive than most of the automotive antifreezes and can be bought in pre-diluted form for less than $10/gal at most truck stops.
 

Rick

Moderator
Staff member
Welcome to the forum BHuij

I'm curious if you've tested bullets at 30 BHN and if this level of hardness is needed. 30 is doable with CWW, I've done it many, many times but my testing indicated that too much of a good thing isn't necessary a good thing. Accuracy fell off as the hardness increased into the 20's. This wasn't with 22's and it wasn't with PC'd bullets.
 

M3845708Bama

Active Member
Adding some copper will help keep bullets together and adding Roto metal supe r hard or hard shot will make harder. Combination of the two should address your issues
 

popper

Well-Known Member
Drop in ice water (cubes melted) from 400F oven after an hour (guaratees H.T.) - you can go higher but watch for slump and shorter time, I just don't rush it. Wait 3-4 days before shooting.
 

yodogsandman

Well-Known Member
I've HT'd in the oven for an hour at 425*F, then electrostatically sprayed the bullets with PC and returned them to the oven (set down to 400*F). After 10 minute, quenched them all in ice water. It worked but, the PC coating was thick.
 

fiver

Well-Known Member
you don't need AR bullets that hard.
linotype lost accuracy for me, half that was much more accurate.
 

Reloader762

Active Member
I'm going to answer your question with several different scenario's so you can get the idea of what quenching vs not quenching PC bullets does to the final BHN. Alloy used COWW's with an as cast BHN of 12.

1. If you air cool your bullets when cast then PC them an allow them to air cool again the second time there is no change in the as cast BHN of the bullet.

2. If you air cool your bullets when cast then PC them and quench them right out of the toaster oven they will gain a hardness of about 75% over the as cast BHN.

3. If you quench your bullets out of the mold to begin with then PC them and allow them to air cool they will soften around 50% from the original first quenching BHN.

4. If you quench your bullets out of the mold to begin with then PC them and quench them right out of the toaster over a second time you only loose around 15% hardness from the first quenching.
 

BHuij

Active Member
Awesome info from everyone, thanks for all the replies.

A few questions--

1) I have heard of adding a small amount of copper to the alloy to get super hard bullets - hard due to alloy mix, even air cooled, rather than relying on a HT/Q. What is the easiest and/or least expensive way to add copper to the alloy? Last I checked, copper melts at a significantly higher temperature than my lead pot is capable of providing.

2) Those of you shooting HV .223 cast bullets out of AR-15s, what have you found to be a good target BHN range? 30 is probably higher than I need, but I'm interested in establishing for myself the strongest bullet I can get using COWW alloy (which I get lots of for free), and also powder coating, which complicates the hardening significantly.
 

Ian

Well-Known Member
Lots of people push up near jacketed fps with water-quenched wheel weight alloy. It's good for about 45K psi. Making the bullets as hard as diamonds doesn't solve the real problem, which is getting and keeping the bullets perfectly point-on straight as they go through the barrel.
 

fiver

Well-Known Member
BHN 15.
a mish mash up of either 2/6/92 or a short side clone of lyman's 5/5/90 type alloy.
the 223 isn't that hard but it takes effort and there is no magic short cut.
 

BHuij

Active Member
Copper isn't for a harder bullet but rather one that is tougher.
Right, and forgive my muddling of already confusing terminology here. For the purposes of this thread, when I say "harder," "stronger" "tougher" I am generally referring to a bullet that is less likely to fragment or deform given high chamber pressures, high velocities, or sudden impacts.

I am reading of people who seemed to be on the cusp of casting a lead/babbit/copper alloy bullet in .223 that could be treated for all intents and purposes exactly like a commercially purchased FMJ projectile. That's probably harder than I need, but it's something I'm interested in achieving, if for no other reason than the pursuit of knowledge and experience :D

So where does one source babbit, and is it possible to add copper to an alloy using a standard Lee production pot, or am I going to need to come up with a hotter crucible to do serious experiments with copper/babbit/lead alloys?
 

fiver

Well-Known Member
simplest way to get it in an alloy.^^^^

you only need a small percentage. 0.3% is enough to get the good without getting the negative affects.
 

BHuij

Active Member
By my back-of-the-napkin math, a single 1lb ingot of grade 3 babbit alloyed to make 27 total pounds of .3% bullet alloy raises my cost per bullet from $0.00 (free COWW alloy) to roughly $0.008/bullet using liberal estimates of weight per projectile (60 grains from the Lee 55gr mold). If this alloy will behave essentially like an FMJ in terms of how fast I can push it, I'm still doing a lot better cost wise than $0.07/bullet for commercial FMJs. This is appealing because in theory with this alloy it's just a "cast, air cool, lube, shoot" process to get jacketed performance, rather than "cast, air cool, heat treat + powder coat, hope PC isn't ruined by excessive heat, allow 1-2 weeks to age harden" process.

With alloy this tough, does a gas check become unnecessary? Or will accuracy suffer by omitting it? What about lube? What would be the approximate BHN?
 
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