What temperature to cook off a primer?


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essayons21
July 8, 2011, 11:21 AM
So I had a couple bags full of miscellaneous range-pickup brass, mostly .45 and .40. It was a muddy wet day, and it has been sitting in the bags for a few months (work has been keeping me busy), so needless to say it was all pretty gross. I tossed the lot of it in my ultrasonic cleaner to get most of the crud off before it goes in the resizing dies.

After ultrasonic cleaning, I usually put my brass on a tray in the oven at 225 degrees for 15-20 minutes to dry it off.

I just pulled the tray out of the oven and started sorting through it, and I found two live .22 LR rounds still hot from the oven. Yikes! I have no idea how they got in there, maybe when one of my shooting buddies was helping me pick up brass he threw them in there. I have been accused of being a notorious scrounger when it comes to brass and ammo, but I'm not so cheap that I pick out individual .22 LR rounds out of the mud.

So the question is, at what temperature will most primers "cook off"? Apparently 225 is too low, I know that campfires (~1000 degrees) are hot enough.

Anybody know?

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Owen Sparks
July 8, 2011, 11:41 AM
I left an open box of 50 rounds of .45ACP sitting in direct sunlight 1n 98 degree weather at a pistol match once. They got so hot that they were physically uncomfortable to handle and I almost could not load them onto my magazines because they were burning my fingers but they did not go off.

ny32182
July 8, 2011, 11:48 AM
The Mythbusters tested several rounds in an oven, and most cooked off at a registered temperature of about 400 degrees if I remember correctly. Not sure if that would be the primer or powder going first. Since the temp in the oven was increasing relatively rapidly I would suspect that the actual cookoff temp of the primer/powder would be slightly under the registered oven temp. Based on that info, I'd bet a steady state temp in the upper 300's would be close to the line.

However, I'm sure it depends on the exact primer and powder in question, and personally I would not make a habit of sticking live rounds in the oven at 225.

roadchoad
July 8, 2011, 11:48 AM
edit -I was wrong...

roadchoad
July 8, 2011, 12:02 PM
Posted by Target Shooter:

Black Powder will ignite spontaneously at 300 degrees Celsius or 572 degrees Fahrenheit.
Single Base Smokeless Powder will ignite spontaneously at 500 degrees Celsius or 932 degrees Fahrenheit.
Double Base Smokeless Powder will ignite spontaneously at 400 degrees Celsius or 752 degrees Fahrenheit.
Primer Compounds:
Mercury Fulminate will ignite spontaneously at 180 degrees Celsius or 356 degrees Fahrenheit.
Lead Azide will ignite spontaneously at 245 degrees Celsius or 473 degrees Fahrenheit.
Lead Styphnate (Trizinate) will ignite spontaneously at 180 degrees Celsius or 356 degrees Fahrenheit.

FROGO207
July 9, 2011, 10:03 AM
Well I am sure that you dried out those .22 rounds if they were wet previously.:D I would inspect my brass closer than you have been before that step in the future if it were me.;) Specially if friends are helping. When drying my brass I try to keep it at 125 degrees or less (sunlight if possible) if I can to reduce stress on the brass. Does this matter?? I am happier if I do it this way and my ammo is happier if I am careful when I make it.:D YMMV

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