Ejected Brass Temperature

[Skinnedknuckles]

I'm experiencing something I can't explain and I hope someone can help. I'm reloading for both a Remington 7400 and a T/C Compass, both in .30-06. Interestingly, both like almost exactly the same load.

When I shoot the Compass (bolt action), the ejected brass is almost cool to the touch and very easy to hold in my hand right out of the chamber. The brass from the 7400 (semi-auto) will just about blister my hand if I try to pick it up too quickly. Is it because some hot gas follows the brass our of the 7400 chamber, heating it up?

 

[Laphroaig]

All semi-autos eject hot brass. My theory is a) it comes out almost before the bullet leaves the barrel so its still warm from the combustion, and b) friction between the expanded brass and chamber.

 

[whughett]

And the quicker you shoot the hotter it is. I’ve experienced mild facial burns from hot brass when my GoldCup bounces brass off my forehead. One one occasion a shell lodged behind my eye glass frame. That one left a mark.

 

[mcb]

Its all about thermal conductivity and dwell time in the chamber. With a bolt gun (or any manually operate gun) the time in the chamber is long enough to allow most of the heat to transfer to the barrel, even if you try to cycle it fast it still has a much much longer dwell time in the chamber then the semi-auto. In a semi-auto it only has a few millisecond to transfer the heat to the barrel and thus comes out much hotter.

 

[jmorris]

That’s one good thing about the mini 14 ranch rifle, by the time you can get to the ejected case, it can’t burn you.

With machineguns, the chamber can become so hot that a round can be thermally ignited, it’s called “cooking off a round”.

Start both with a cold chamber and fire one shot, catch the case in a basket right beside the rifle and check their temp.

 

[tightgroup tiger]

The receiver is soaking up the heat from a bolt action because most people look at their target before they eject the empty.
The semi-auto kicks it out immediately and if you don't like picking up brass off the ground and your sitting at a bench with your rifle on a sandbag and one hand beside the bolt to catch the brass, it's going to be really hot when it comes out.
I like jmorris's statement on the mini 14. That's funny!

 

[Walkalong]

That’s one good thing about the mini 14 ranch rifle, by the time you can get to the ejected case, it can’t burn you.

Amen to that.

 

[FROGO207]

What do you expect with a Mini 14. And having to get NASA involved and clearance due to low earth orbit and all! Sheesh

 

[243winxb]

Powder burns around 4500 degrees.

 

[cfullgraf]

Not to be a broken record on the answers, but basically what everyone has said is spot on.

jmorris' comment on the Mini 14 is great. I have a couple hand guns that fall in that category.

 

[mdi]

Haven't fired a Mini 14, but by the time I put my Garand down, get up and find a case, it's cold...

 

[ATLDave]

On a related note, one of the big technical challenges to caseless ammo is that brass acts as a heat sink, carrying heat away from the firearm when it is ejected. Caseless ammo just leaves all the heat in the action and barrel. When you're talking about combat guns, particularly full-auto guns, that is a huge issue.

 

[1KPerDay]

That’s one good thing about the mini 14 ranch rifle, by the time you can get to the ejected case, it can’t burn you.

And it’s encased in a protective layer of quartzite

 

[Dudedog]

That’s one good thing about the mini 14 ranch rifle, by the time you can get to the ejected case, it can’t burn you

By the time I find mine they have had plenty of time to cool, heck even if you see where they land it takes five minutes to walk to them
Nice positive ejection on my Mini 14