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Old August 6, 2012, 01:03 PM   #1
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Why the difference between .204 and .223?

I reload for my .204 bolt action and .223 AR15. Even though the .204 uses more powder, the cartridge is fairly cool to touch immediatly after removal. However, when the .223 comes whizzing out of my AR, the cartridge will melt the grooves off your fingertips even after some time. Is that from the gases escaping back into the breech area during ejection or something else? Thanks.
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Old August 6, 2012, 01:18 PM   #2
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The .204 cases, even if ejected as fast as you can manage, are in the chamber longer and transfer more heat to the chamber/barrel.
The .223 cases, on the other hand, are violently expelled from the AR just milliseconds after the bullet leaves the barrel. There is no time for the chamber to soak up the heat in the brass case.

Arguments could be made about different powders acting differently, as well; but the actual affect would be trivial.
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Old August 6, 2012, 01:49 PM   #3
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I think FM probably nailed it. I have noticed the same difference you did between my .223 bolt gun and my .223/5.56 AR shooting the same ammo.
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Old August 7, 2012, 03:16 AM   #4
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im almost positive it actually does this on purpose, so you dont over heat the gun as easily, it being a military rifle and all.

thats one of the main problems with caseless ammo is over heating, they dont have the brass to carry a lot of that heat away from the gun
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Old August 7, 2012, 11:44 AM   #5
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Yep, what Frankenmauser said.

The chamber and barrel is a giant heatsink, far more massive than the case. Even when they're "hot", they're much cooler than the case is immediately after firing and they cool it almost instantly.

You literally can not work a bolt fast enough to have the case hot enough to burn you, at least anytime I've ever tried it.

With a semi-auto, the heat isn't even done happening yet (more or less) when extraction begins, no time to cool.

You could compare a 50BMG bolt action to a 22LR semi, same thing. It's not a cartridge specific condition.
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Old August 7, 2012, 06:43 PM   #6
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Cool, I had noticed the same thing with my .308 win bolt vs my dad's 30-06 semi auto.... I had just figured it was because the 30-06 is more powerful, but didnt understand how the cases could be SO MUCH HOTTER after firing, since 30-06 isnt THAT much more powerful than .308win.....

Longer time in the chamber makes more sense....
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Old August 7, 2012, 08:39 PM   #7
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Noticed the same phenomena when i shot my 22 bolt rifle vs my 22 semi that brass is HOT...
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