Barrel heat

[Wow]

I found this neat little document of a study done by the army on M4 barrel heat. The test involved firing 280 rounds full auto in the span of a minute and a half and then letting it cool down.

Here are the two most interesting pages from it (I think).

https://i.imgur.com/RxKtopU.png

RxKtopU.png

https://i.imgur.com/ZHQug90.png

ZHQug90.png

What is interesting is that the hottest point is 4" into the barrel. I would have guessed the gas block area would be hottest.

Source: https://apps.dtic.mil/sti/pdfs/ADA285699.pdf
Document name: AD-A285 699

[lysander]

I found this neat little document of a study done by the army on M4 barrel heat. The test involved firing 280 rounds full auto in the span of a minute and a half and then letting it cool down.

Here are the two most interesting pages from it (I think).

https://i.imgur.com/RxKtopU.png

RxKtopU.png

https://i.imgur.com/ZHQug90.png

ZHQug90.png

What is interesting is that the hottest point is 4" into the barrel. I would have guessed the gas block area would be hottest.

Source: https://apps.dtic.mil/sti/pdfs/ADA285699.pdf
Document name: AD-A285 699

The gas is hotter the further toward the breech you go.

The thinner parts of the barrel will get the hottest.

Therefore the thinnest part of the barrel closest to the breech will get the hottest, which is about 4 inches from the breech.

[Stickman]

This is why barrels which are thicker towards the breech and taper are better profiles.