[Afy]

Why are cases fired from a semi auto hotter to touch than those from a bolt action? Especially since the semi cases spend less time in the chamber?

Or is that the reason?

:confused:

[matrem]

I've not noticed that. Maybe because I've not had a case from a bolt gun hit me(southpaw) in the neck and continue down my shirt?

[edelbrock]

I have not noticed either. Maybe for the reasons listed above.

[SquirrelNuts]

I can't tell a difference.

[Steve C]

Likely because spending longer time in the chamber allows more heat to transfer to the larger steel chamber, barrel and bolt which would act as a heat sink.

[351 WINCHESTER]

Since the semi auto extracts and ejects much faster than the bolt gun I figure friction has a lot to do with the heat.

[Otto]

I assume that the repeated firings in the semi-auto heats up the chamber to a higher temperature than that of a bolt action's cooler chamber. Think of the chamber as an oven.

[Ol` Joe]

The steel in the chamber sucks the heat out of the brass case faster then air does. The longer time spent chambered in a bolt or other type action allows the brass to transfer its heat

[Jenrick]

What Ol'Joe said. Brass transfers heat quickly (pull a glass dish out of the oven at 500 degrees and see if you can handle it in less then a minute like you can brass). Air is a very poor heat conductor, solid metal however is a very good one. The chamber, bolt, etc. get a lot of the heat transfered to them due to the longer ejection time. A semi-auto pops the casing out into the air where it takes much longer to cool down.

-Jenrick

[Walkalong]

What Ol'Joe said.Yep..

[Nate1778]

This is simply a guess as I have not really paid attention to it either. I think with a Semi-auto your tendency is to pull the trigger a bit more frequently. even though the round is not in the chamber for very long the additional shots warm the barrel fairly quick. I view the bolt gun as a more of a "shoot, think, observe" then shoot again type gun, not shot as frequently as a semi. If it is a gas actuated gun you also have that working against you, now you have more steel being exposed to heat. More mass the longer it takes to cool. I know my old AK would get hot quick and stay that way for a while.

[rcmodel]

The brass is not in the chamber of a semi-auto long enough for the barrel to act as a heat sink and pull the heat out of the case.

The ability of the brass to transfer heat out of a gun is a factor figured into machinegun design.

Big problems arose with caseless ammo development because there was no metal case to remove heat from the gun as fast as it was being generated.

Put another way, a bolt gun firing 50 - 100 rounds quickly will get the barrel way hotter then a semi-auto firing the same number of rounds in the same time frame. Because no matter how fast you open the bolt action, the hot case is in the chamber transferring heat longer then in an auto.

BTW: I doubt friction plays any factor.
When the bullet leaves the barrel and the bolt unlocks to begin extraction, pressure has dropped, and the case has already relaxed it's grip on the chamber. It is barely in light contact with the chamber before extraction can occur.

rc