Just curious if anyone knows the cookoff threshold for AK type firearms, either 7.62x39 or 5.45.  Considering their service rounds are substantially lower pressure than Western counterparts, I wonder what practical effect that has on barrel heating.

This guy tortures various models on his channel to their breaking point

https://youtu.be/Io7Zztghdno

Thanks, but I've seen those; while it's cool how much abuse those AKs can take, the videos I have seen have them just dumping mag after mag on full auto.  You won't likely get much cooking off that way as the round is getting fired right after being chambered.

Check the Kalashnikov concern videos they are on the site.

JesseH1234 said:

Just curious if anyone knows the cookoff threshold for AK type firearms, either 7.62x39 or 5.45.  Considering their service rounds are substantially lower pressure than Western counterparts, I wonder what practical effect that has on barrel heating.

Being lacquered steel cases the heat transfer is also going to be a lot slower than brass as well. In a practical context, more ammunition than anyone is likely to carry into combat and even in a Wanat situation the gun will clog with lacquer before it cooks off. 

I've always wondered about the H&K machine guns (HK 21/23). These are belt-fed guns, firing at a high cyclic rate, yet they fire from a closed bolt. Everybody else's LMG's fires from the open bolt. Isn't cook-off a problem in these guns?

https://en.m.wikipedia.org/wiki/Heckler_%26_Koch_HK21

Well according to Wiki the HK21E can do 1,000 rds; not sure I buy that , but simce youre supposed to swap barrels every 2-300 rds it might not be much of an issue.

There existed a promotional HK movie from the seventies, showing an HK21 firing one long belt of 500 cartridges of mixed type, including some with steel cases.  Standing one very long burst (with the chamber empty at the end) is one thing.

Cook-off exposure is another thing. Needed is the number of rounds one can fire in a relatively short time, without the danger of the "next" cartridge sitting in the chamber to cook-off. This number is not given in the HK21 manual as far as I know. 

The manual says to change the HK21 barrel after 150 rounds fired [the same number as in Bundeswehr MG3 manual, although the MG3 acceptance procedure used 250 round bursts]. I understand this as meaning that up to 150 rounds there is no cook-off danger with HK21.   

Well, these guns have been in production for almost 60 years and H&K have not changed the firing system, so, cook-off must not be a problem. And the barrel change system is very good.

Yeah I'm with you, hence my original question.  It's one thing to dump mag/belt one after the other, but the real question is at what point does that closed bolt start making decisions on its own.