Tracking BHN of heat-treated COWW over time

fiver

Well-Known Member
#22
I know the powder I'm using goes wet at 375-380.
I like to start my timer when I see that happen and let the oven come up and over shoot 400 a little right at the end.
if I wanted to I bet I could hold the 380-5 area for a full hour with fresh powder and go straight to water and get the powder to set up properly.
I know a few guys have run lower for longer and had good results with their powder too.
 
#23
Ian, you're more than welcome to run any tests you want. I'm going to be sticking with 100% pure COWW with no additives for now. Basically since that's the only alloy I have to work with.
 

Kevin Stenberg

Well-Known Member
#24
Huij That wasn't as bad a read as you hinted it was. I found the information well layd out, informative an interesting.
I probably missed it. Your how to disription on HT. Were bullets touching each other in the tuna can? Was the bottom of the tuna can perferated so the water could touch the bullet faster than having it flow over the top of the submerged can and then fill in around the bullets?
 

fiver

Well-Known Member
#25
I can't answer for him.
but I wouldn't pile them up or let them touch in a big glob.
and I would just dump the whole thing in the water top down the can probably wouldn't even go in.

the key is to do everything the same, same water temp, same temp setting on the oven, same time from oven to water.
1-2 BHN difference from batch to batch isn't the end of the world, but it isn't that hard to make them all so super close you can just dump everything [various batches] in a big bucket and use them all 6 months to a year later without fear.
 

popper

Active Member
#26
For quenching, it is the cooling rate that determines hardness. Basically the amount of heat in the bullet, conductivity of the material and change in temp. Yes there is steam created when quenching which does reduce the rate but nothing we can do about that with H2O. The alloy doesn't have enough 'other' stuff in it to affect the process but of course the result BHN will be affected. Reverse the process for heating. PC baking gets the bullet up to temp in ~15 min. Then you have to add time for the molecular mobility which appears to be ~ 1 hr for 'normal' weight bullets. If casting those really big ones, I'd add some time.
BHN readings for high BHN are not too accurate due to 'spring back' of high Sb alloys. Additionally, the smaller 'crater' leaves a higher uncertainty in the measurement.
I've been PC cooking on a hot plate as I stand them up, just easier. Temp control is more difficult and the target shows it (HV rifle) so I now re-cook in the oven. WD for both processes. Easy and can't hurt.
 
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#27
Huij That wasn't as bad a read as you hinted it was. I found the information well layd out, informative an interesting.
I probably missed it. Your how to disription on HT. Were bullets touching each other in the tuna can? Was the bottom of the tuna can perferated so the water could touch the bullet faster than having it flow over the top of the submerged can and then fill in around the bullets?
Glad it wasn't hard to understand. Bullets were not touching each other to the extent possible. It's not impossible a few of them did touch while being baked, and they almost certainly touched while being whisked over to the water bucket. Can was not perforated, but it still only took a split second to get the bullets completely submerged as I quickly shoved them down to the bottom of the bucket.