Does air-cooled COWW alloy take a few days for BHN to stabilize?

BHuij

Active Member
Hey everyone--

I'm doing some testing to find what works for me to hit various targets for BHN using COWW alloy. Effectively, I'm testing different times and temperatures for heat treating and quenching bullets of various calibers, and tracking their BHN at the 0-day, 1-day, 7-day, 14-day and 60-day marks.

Later, I'll also be trying some various methods of powder coating and quenching to see if I can get higher BHNs in some of my powder coated bullets without having to play around with different alloys.

Yesterday I cast up a bunch of bullets from a number of molds, all using the same pot of 100% COWW alloy. These were allowed to air cool. Within 6 hours or so of casting the bullets, I measured the BHN on some of them, and it averaged out to about 8 BHN, softer than I was expecting for COWW. This morning (~18 hours after casting), I measured several more from the same bag and they were averaging about 9.5, which seems closer to what most people report for this alloy.

I'm aware that after heat treating/quenching, it takes bullets anywhere from several days to upwards of 2 weeks to reach their "peak" BHN, depending on arsenic content in the alloy, and some other factors. However, my results so far suggest that even air-cooled COWW bullets might take at least a day or so to get to their "actual" base BHN, maybe longer. I'll have to confirm with further testing. Has anybody else ever noticed this?
 

fiver

Well-Known Member
7-10 days is my minimum wait time for air cooled, a month for water quenched.
they might be done a little sooner, but the entire batch seems to settle into a narrower window in that amount of time.
 

BHuij

Active Member
Unexpected, but makes sense. I'll continue taking readings on my air-cooled WW to see when it stops moving.
 

Ian

Well-Known Member
Test every day for a week, and every three days for the following week. AC-COWW typically start out 7-8 bhn and end up 12-13, may take two weeks to stabilize and in a few months there may be a tiny bit more hardening/growth.
 

BHuij

Active Member
Please correct me if I'm wrong, but I'm guessing what's happening here is that the molten alloy has fairly well-mixed components (lead, tin, antimony), which, when air cooled, slowly form dendrites over the course of a couple of weeks or so to stabilize on the "final" hardness of 12ish BHN?

If that's the case, when I take a month-old air cooled COWW bullet and powder coat it at 400 degrees for 20 minutes, should I expect that process to start over somewhat? Perhaps the freshly-PC'd bullet will again start in the range of 8 BHN and slowly work its way back to 12ish?
 

Ian

Well-Known Member
Yes, somewhat. Might not get as soft as when first cast, and might not get as hard after coating, particularly if quenched. I think Bama noted trends of achieving about 80% possible hardness when water-quenching from the coating oven.

Google "precipitation hardening", that's what "hardens" the alloy with time.
 

BHuij

Active Member
Yeah, that is in general terms what I was expecting from attempts to HT/Q after powder coating - perhaps not as hard as bare lead would be after 2 weeks, but hopefully hard enough to use in higher velocity applications. Initially I worried that 60+ minutes at 425 degrees F would mess up the powder coat itself, and maybe it will, but I won't know until I've tried it.

But without a lubrisizer or any realistic expectation of getting one in the next few years, I want to stick with powder coat as much as possible. I made up a batch of Felix lube to try in 7.62x54R as well as .223 with some heat-treat hardened projectiles, since my normal powder coating was annealing things and undoing the HT/Q. I'll be firing them tomorrow to see how they do. But pan lubing was an enormous PITA for the fat .30s, and about twice as bad for the .223s.

Unless these bullets do something really special, and something I find completely impossible to replicate using powder coated projectiles, I'll be steering clear of pan lubing for the foreseeable future.

Hence experimentation to see what kind of heat treating is possible after powder coating.

Thanks all for confirming what I found. I'll continue my tests and post my findings here.
 

Ian

Well-Known Member
Finger-lube. Some of us have become expert at it doing hundreds of lube tests over the years, much faster and better than pan lubing.
 

BHuij

Active Member
I ended up doing that with a few of mine. That Felix lube is just so unbelievably sticky, it was a mess. I still ended up needing to force the bullets through a shell casing with the headstamp removed just to slice the excess lube off and leave lube only in the grooves. Got all over my hands.

Is there some magic technique you can point me towards, or am I using a lube less suited for finger lubing? :D
 

popper

Well-Known Member
Above 400F for an hour, then into ice water. Size the next day. Stabilized in a week. Yes, short time cooking will get you back close to AC. Neither Smokes or HF powders are damages up to 450F (for an hour). The alloy doesn't like it though, have to watch for slump.
Edit: After cooking @ 400 for an hour, dropped into ice water, then quickly into freeezer. After overnite in freezer, same as ice water quenched. Getting temp as high as possible without slump does make a difference, ~40F diff. gives a big BHN difference..
 
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BHuij

Active Member
So I think I'm going to do a battery of tests where I check the effect of temperature and time of heat treat before quenching the bullets, both before and after powder coating.

I was going to use some fat .30 bullets that I use in my Mosin, as well as double checking that my results would be the same on the .22 cal bullets I use in my AR-15.

But as long as the time is long enough for the .30 bullets to be heated through before they're quenched, the BHN over time shouldn't differ from the .22 bullets, right? Those little 55gr projectiles are a pain to test in the hardness tester and I don't want to duplicate my efforts if it's not useful. Think I could get away with just standardizing on the .30 cal projectiles, make sure I'm baking for at least an hour or so, and then assume results are functionally identical for bullets out of other molds as well?
 

Rick

Moderator
Staff member
How fast they cool is what will harden heat treated Pb/Sb alloys. The 30 caliber will have more mass than the 22 but if quenched the same and of the same alloy I would think they would be pretty close. I've never done the powder coating but I did get a chart started on various oven temps for heat treating, you can see it here. I've also never compared final BHN between small bullets and larger ones, your results will be interesting.

Heat treating Pb/Sb alloys
 

BHuij

Active Member
Yeah that LASC chart what was made me want to "calibrate" my own BHN. And particularly see what I can get out of HT/Q powder coated bullets. I'll be sure to share my results, but it's going to be a while before testing is done haha.
 

Roger Allen

Active Member
I am in no way scientific like Ian and the such but I will say I air cool my alloy mixtures for 90 percent of what I do, I have waited 2 weeks which I swear is what I tend to do w everything, I also have gotten super excited w a 45-70 mold in plain based form and shot the bullets half a day later after powdercoating and I will say........in 45-70 it made no diff at all. In my 35 rem I’m really scared to find failure because the pressres excessed what I considered my comfort envelope but I did shoot those a week and a half later got my most excellent groups (we are talking a basic mix of 50/50 clip on wheel weight/ pure-range lead mix). I’d venture to say that 1. Number one is fit and design and number two is hardness. Not too hard as to antimony wash your barrel and never seal and soft enough to seal and to expand on animals when you hit that shoulder bone and push your way to victory. I’ve killed lots of poor deer w that mix and I’d say a lot of us are using way too hard a alloy in fear.......if also say I’ve shot 1/2 a day after air cooling and seen the same results as 2 week stabilizing. Now i will also put a rider in here I don’t shoot 1/4 inch groups often w my cast guns but I will say I’m a great shot and I’ve nailed targets 120 yards away w 1/2 inch groups w 14.5 inches of dope w my vortex diamond back w my West Virginia logic w out using fancy micro waxes and just throwing my alloy mix w your super enjoyable 45-45-10 most loved and appreciated w 2 week stabilized alloy shot from marine tex bedded rifle shot from a gun case rest and Russian primers so I’d say I’m getting at is enjoy, use the experience to help push you to success but ladder test, enjoy what you do, fit your bullets to your rifle, start your bullets as long as you can into your chamber, don’t blow yourself up, and reloading won’t save you money so shoot often w your savings......buy thousands of molds!!!!!
 
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BHuij

Active Member
I'm actually right in the middle of doing some fairly rigorous hardness tests with various experimental groups, including one control group where I powder coated and that's it. I've been tracking that BHN for 8 days so far and it's still going up. I suspect that PCing just makes the alloy strength itself slightly less important.
 

fiver

Well-Known Member
I'm gonna speak for myself and Ian on this part.
he will correct me if I'm wrong..LOL

but I can say we wait because things do change slightly.
the reason we wait is I bet we have both been assbit down the road by bullets that have grown slightly, and by slight enough changes in the BHN to make group sizes change.

I remember one particular instance where I used 'FRESH' bullets from a new to me mold in my 30-30 for a load work up the week before the deer hunt then packed the loaded ammo away with the rifle for the season.
the following year I took the same rifle and ammo out again and just about had to use 2 hands to get a round to chamber opening morning after hiking in the day before and was scared to try and get the round back out of the rifle until the hunting trip was over.
I just shot the round into a tree when I got back near the truck, but I had a loaded round in my rifle for 4 days and nights and no follow up shot in the magazine.
 

Reloader762

Member
For many years I've been doing most of my casting in the winter months when it's much cooler, temps in the 90's and humidity in the 75+ range makes it no fun to sit over a lead pot. I don't really shoot enough to use up my supply so I always have around 1K or so bullets on hand for ever caliber I shoot that have been setting idle for at least six months to a year. Most all my bullets are cast from either 50/50 WW/Lead or straight WW's and air cooled,I generally don't size those till needed. If I water quench or PC and quench I generally size those bullets in the same day and let them sit for a few months before loading.

I haven't had any issues with bullets growing or shrinking or groups changing doing things the way I do them. I'm sure there are some changes that take place but evidently it's nothing sufficient for the type shooting I do.