Reheating/recuring PC boolits?

[THG]

Can PCed boolits be reheated to effectively cure/recure the PC? Or did I just ruin 2,000 precious cast boolits?

I powder coated my first boolits today. Two Thousand 125 grain 9mm PCed with Smokes Signal Blue, purchased way back in 2016. I was very happy with how the process went. Water quenched and sized to .356.
I loaded up 200 to test and was dumbfounded that half of them tumbled wildly!

I shot a magazine of the exact boolet sized .356 and lubed with Magma Lube. All these uncoated boolits grouped very well as usual.

I did a search and saw that I may not have held them at 400 degrees long enough. My oven was not holding the temperature very well, 375-425.

[bmortell]

i cant see why that would make them be unstable. id think it more likely to be a hardness difference between the 2 methods or something like that. could also catch one of each and see if there's anything to note

[bangerjim]

Once PC is cured you cannot re-cure it......as far as I know. Try it and see...I have never had the need to do it, as my cures are always to spec.

You can always re-melt and start over! That is the nice thing about our lead hobby.....mistakes are easy to correct.

Now you know why I always say: "buy a quality high-end digital convection oven"!!!!!!!

banger

[Finster101]

I can't see PC causing the tumbling. Why did you water drop them? Were your conventional lubed bullets quenched as well?

[popper]

Quench only works after PC cooking. Tumbling is mostly due to size.

[Finster101]

[QUOTE=popper;5059600]Quench only works after PC cooking. "


That's news to me.

[bangerjim]

[QUOTE=Finster101;5059606]

Quench only works after PC cooking. "


That's news to me.

Water-dropping Sb-containing boolits right out of the mold (> 600F most times) is the old-school way of "cheating" to get hardness greater than the actual alloy mix will yield, as you know, when using old grease-based lubes.

When you PC and reheat/bake the boolits to only 400F for 20 minutes (10 is sufficient after flow, but so many are using an unneeded 20 minutes) the reheating removes most, if not all, the hardness you gained from the original water drop right out of the mold. And 400F is not hot enough to gain much, if any, Sb-related hardness after the PC bake. So why bother????????

I have found I can cast & shoot pretty much anything from .223 thru 45LC with standard mixed hardness of 10-12 and NOT water-dropped, and then PD'd............with excellent results..........no smoke, no leading, no dirty barrels, no sticky boolits.

banger

[Conditor22]

why do you think the boolits/PC isn't cured?
did you do the hammer test?
were the lubed boolits the same alloy, size, and shot at the same velocity?
Is this a toaster or convection type oven?
I started with a toaster oven (for 1 day ) then bought a cheap new convection oven. Toaster ovens work but you really have to watch the temperature and only bake small batches. I've been using the cheap new convection oven for several years and many thousand pounds of boolits, It will do 8# of boolits per bake.
I found 2 (two) larger 2-shelf convection ovens at thrift stores for <$20

I'm not a chemical engineer so I bake my powder coating to the manufacturer's specifications to get a full cure

Countertop ovens are notorious for not holding the set temperature you need to test the temperature setting with an oven thermometer and adjust the setting until it reads 400°. this setting will also vary with the ambient room temperature.
I loved the PID I put on my casting pot so much that I put one on my oven. Now I don't have to worry about temperatures anymore

[Petander]

Did they have a plastic smell when fired? What kind of oven, how many baked at once?

EDIT: The good old expander question:

Did you pull any loaded bullets to see if the coating stays on and the loaded bullet size stays right?

I started with a toaster oven (for 1 day ) then bought a cheap new convection oven. Toaster ovens work but you really have to watch the temperature and only bake small batches. I've been using the cheap new convection oven for several years and many thousand pounds of boolits, It will do 8# of boolits per bake...


... I'm not a chemical engineer so I bake my powder coating to the manufacturer's specifications to get a full cure

That's pretty much my story as well. I use a 2 kW oven now, 8 lbs max. Uneven bake is hard to detect until you shoot them and I've been there already... enough. I bake everything a little extra time/degrees now,every oven has cold/hot spots. Different powders have different bake recommendations.

[THG]

All responses much appreciated.
I water drop simply to get a harder bullet with lead from all kinds of sources. Most of it is not clip on wheel weights. The goal is to generate as many useable 9mm practice rounds as cheaply as possible, so I can get the kids and grandkids out shooting once a month. 1000 rounds goes fast.
I have been buying bullets to shoot competition from two local producers, one Hi-Tek one PC.
I was hoping to be able to make a better quality bullet for competition to save some money, also these guys are running way behind these days.

The oven is a convection oven. Oster extra large countertop oven madel TSSTTVXLDG-001
I did two trays of 250, about 9# total.
I water quenched them because they dropped off the screen trays so easily.
Both PC and plain bullets are the same alloy, mold, quenched etc.
I pulled bullets last night as suggested. The die is .356 the PC bullet measured .355!
Changed to .357. Bullets measure.356. Loaded 50 to test later today.
Will report back.

[popper]

I'll state this again - if you cook coated bullets it must be done for ~1 hr and then dropped into cold water to get ANY heat treating! A 10 min cook drops the bhn back down to AC hardness. A soft bullet in 9mm case will get swaged down by the case and will size smaller due to less 'springback' of the soft alloy. Just plain physics. Long cook time hasn't hurt any PC I've tried, it does darken HiTek.

[bmortell]

if you cook coated bullets it must be done for ~1 hr and then dropped into cold water to get ANY heat treating!

Thats just not true. this is the difference between water drop vs air cool after a normal 400f 20 min cook. Bullets are WW fired at water at 1550 fps. Maybe could squeze out 5% more hardness or so by going an hour but its obviously working as is

also this chart people talk about below. in the youtube video thats from he states to be cooking only 15 min in the video description

[joe leadslinger]

If you follow the directions for the PC cook times and quench after pc'ing your bhn will increase.

[bangerjim]

But...............PC'ing is one of the MAJOR reasons we do to NOT need hard lead anymore. 10-12 + PC works in everything I shoot perfectly, especially in 9mm/38 sp/40s&w/44/45lc. I mix all my alloys for air-cooled hardness and do not rely on some voodoo hardening gain with water dropping.

The old-school rules of hardness went out the window long ago. Fit, not hardness, is the key to good clean shooting. Couple that with the protection of PROPERLY applied PC and you have the best of all worlds - clean barrels, no grease smoke, save on expensive hard alloys, no leading (if fit is proper), no sticky boolits.........and really cool to look at!

Don't get lost in the weeds about hardness. And hey, if you get it wrong, just re-melt and try something different.

I know I sure have!

banger

[popper]

Properly hardened 40sw into a rock pile (frozen road chat pile from 5 ft). Alloy similar to hardball. 95% or better weight retention. Digging in the pile was hard and the 9mm fmj were all bent to crap & some lost jacket.

[reddog81]

A couple of points...
1. Are you sure they were tumbling? Half the time people think a bullet is tumbling it's really just the paper tearing.
2. Is you're barrel leaded up? Accuracy will go out the window with a barrel full of lead. In theory the leading could have been caused by either the lubed bullets or the PC'd bullets.
3. Did the PC'd bullets pass the smash test?
4. I'd try lubing the PC'd bullets before melting them down and recasting.

[THG]

Okay Gents, Problem Solved.
The bullets did pass the smash test.
The bullets run through the .357 die measured .356 and flew straight from 5-15 yards. I shot card board from 5-15 yards and found no tumbling. I shot "Dot Torture" at five yards and shot it as well as ever, one miss with the weak hand.
After 50 rounds, the barrel cleaned up with one patch of solvent followed by a clean patch. That's was easier than my lead bullets.
I do not know why my lead bullets were not tumbling since they were sized in the same .356 die, but it doesn't matter. I'll be running everything through the .357 die.
I am confident that I can load a couple thousand without worry.
Everyone's help and suggestions are appreciated.

[THG]

You were right popper. Went from .356 to .357 problem solved. Thank you.

[Dragonheart]

Problem is the only thing the Smash Test proves is the bond of the PC. It does not answer your question as to the hardness of the polymer. Just because a balloon will stretch doe it mean that it is also hard?

To determine hardness you need to use the Scrape Test. The simple test, developed by a physicist, is to take a razor knife and with the blade held at 90 degrees and with light pressure scrap the polymer. if it easily scraped off then the odds are you do not have a full cure.

if you want to go a step further get some drafting pencils of known hardness like H, 2H, 3H, sharpen to a point and see if they can cut into the polymer when scratched. The powders I use are 2&3H. If you use Prismatic Powder you can find the hardness scale on every powder they sell on their website.

If the polymer has reached full cure then reheating will not make it harder. However, if the polymer has not reached full cure then it can be reheated to the proper time and temperature and reach full cure. This process is called "Partial Cure" and is done intentionally when multiple coats are desired. The first powder coat is cured to the point of full flow, but stopped short at about 300 degrees. Then the second coat is applied and then a full cure, or repeating the partial cure build up process for as many coats as desired.

If in doubt I would suggest doing a "for sure" full cure.

[fredj338]

I'll state this again - if you cook coated bullets it must be done for ~1 hr and then dropped into cold water to get ANY heat treating! A 10 min cook drops the bhn back down to AC hardness. A soft bullet in 9mm case will get swaged down by the case and will size smaller due to less 'springback' of the soft alloy. Just plain physics. Long cook time hasn't hurt any PC I've tried, it does darken HiTek.

I water drop out of the oven & my CabinTree says I get a 3-4bhn pump.
Most tumbling os due to undersized bullet or defect in the base.