??? The Effect of Curing PC VS Bullet Heat Treating

[gman]

Ended up going 20 minutes after I thought about since I go 10 minutes after gloss and the oven gets back to 400. Couldn't help but test one only 3 hours after cooling. Tested 10 bhn. I'll check one Tuesday afternoon and leave the other 3 for when I get back from offshore. That will give 10 days to settle.

 

[gman]

My 70/30 mix air cooled test 13. After PC'ing they test 10.

 

[gman]

I tested another bullet this afternoon. 2 days after heating to 400 for 20 minutes. 10 bhn.

 

[yodogsandman]

How are you testing bullets that are powder coated?

 

[gman]

Same as the uncoated ones. The cabine tree tester goes right through the coating. I've tested them before coating and after to see the change. My coated bullets are not that hard to start so that might make difference.

 

[yodogsandman]

Guess I would have expected a BHN of about 26. That's what the PC coating is supposed to be.

 

[Brad]

The coating is so thin that our devices may not give accurate readings.

 

[yodogsandman]

Probably the only fair way to get an accurate reading would be to cook an uncoated bullet for 20 minutes and test that one.

 

[gman]

That's what I did. Uncoated bullet from batch that tested 19 bhn. 20 minutes at 400 dropped it to 10 bhn. I should get home tomorrow weather permitting. That will give the bullets over a week to stabilize. I'll test them when I get home. Sorry if my other post was unclear.

 

[gman]

Tested the last 3 bullets. BHN was 11, 11 & 12. This from the original 19 bhn.

 

[yodogsandman]

Thank you! Your testing settles it. Guess if I want harder bullets that are PC'd, I'll oven heat treat, coat with PC then quench. That or use a harder alloy to begin with.

 

[Landshark9025]

Interesting.

I wonder if the rapid cooling of PC by quenching it would make it brittle or otherwise affect it negatively.

I'd probably just go with a harder base alloy.

 

[yodogsandman]

I've quenched PC before with no ill effects.

 

[Landshark9025]

Cool, thanks for the reply. If one only wanted to increase the hardness a few points, say from 11 to 14 or so, could you just drop them straight from the PC bake? I know the preferred is to heat to just this side of slump for a minimum of 30 min, but if you were looking for modest improvement, it would SEEM like dropping from the PC bake might get you there.

Disclaimer: I've not tested any of that and am fairly new at the PC and HT/Q games.

Thanks

 

[yodogsandman]

Try it, it can't hurt a thing. When I did it, all I wanted was maximum bullet hardness. The only problem that I ran into was preventing too much PC from melting to the bullet surface. The PC would immediately melt onto the bullets' heated surface making it hard to gauge the thickness.

Most agree that at least a one hour heat soak in the oven gives better results for heat treating.

Heating your bullets to "just this side of slump" will get you the hardest bullets. Heat soaking to a lower temperature will let you determine how hard you want them to be.

Check out this article. I consider it the "gold standard" for info on heat treating.

http://www.lasc.us/HeatTreat.htm

 

[Landshark9025]

I may throw that on the experimentation list at some point. Not sure if I have a need to bring them up a bit harder, but if so, this should work.

 

[fiver]

I don't know how far into the bullet a 20 minute soak would go but I would think even if it was only 1mm you'd have that 1mm hardened.
it would probably be enough to grab the rifling effectively which is why we treat them to begin with.
with the .002 or so coat of powder and the increased bhn of the 'skin' of the bullet you should see a better result.

 

[Rick]

Once the alloy is cured it will be the same harness all the way through. Not possible to surface harden lead. Steel will surface harden but lead doesn't work that way.

 

[popper]

No problem overcooking the PC then WD. I was cooking for 1 hr @ 400F air temp. drop in ice water. No problem but size soon after. Yesterday I did some for 30/30 on a hot plate @ 'indicated' 350F for 20min. HF red glazes ~ 190F. Added a few uncheck/uncoated for testing but no BHN tester. Compared to AC isocore, much harder. This alloy is 5:1 isocore/Pure. Testing done ~8hrs after WD - compare to AC reject (week old) squished in vise. About 3x width of indentation on the AC. Conduction method of cooking works better than convection - no insulating coating & air/Pb interface, thus the lower temp. These were 185gr GC boolits. I do the PB 170s the same.

 

[yodogsandman]

I'd bet that after a week, you'd feel an even greater hardness with your quenched bullets.