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I've been in a fistfight, but nothing serious.

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I am MaximumZero, and I got in three fights this morning before breakfast.

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Total Members Voted: 0

Voting closed: April 02, 2017, 08:55:24 am

[Strife26]

It depends on what you're firing and especially on the rate of fire. Significant heating is pretty much only a thing with automatic or rapid semi fire.

[Erkki]

Anyway, I got a question for the gun-affine folks here: How hot do the chambers of various types of firearms get? Rifles, revolvers, assault rifles in their various modes...

Depends the gun and how much and how rapidly you shoot. An just fired case doesnt tend to be hot at all but the barrel and thus somewhat less so the chamber too can get very warm if one shoots a lot. Just 30-ish or so quick shots can make a rifle barrel so warm you dont really want to grab it by bare hands, maybe even less, depends on the gun and ambient temperature. Thick barrels and heat sinks help. OTOH I've never noticed the barrel of my 22LR to warm much at all, but the rifle barrel gets noticeably warm after just 3 shots.

I think cartridge will cook off at a temperature of 150 degrees celcius. Getting a chambered cartridge there will take a lot of shots, in the cook-off videos they tend to require like 600 or so very rapidly or in full auto.

edit: cookoff risk is  one of the main reasons why machine guns tend to fire from open bolt.

[AzyWng]

Cook-off = heat up to the point where the propellant ignites by itself, right?

[Strife26]

Cook-off = heat up to the point where the propellant ignites by itself, right?

Yes. This is generally only a thing that happens in closed-bolt machine guns and large-bore weapons, although it's possible for it to happen with pretty much any bullet that gets hot enough. Protip: don't throw bullets into campfires.

[Akura]

It also can happen with caseless ammunition. It's one of the main reasons caseless ammunition isn't used much.

[Antioch]

It also can happen with caseless ammunition. It's one of the main reasons caseless ammunition isn't used much.

Caseless ammunition also causes guns to heat up faster, since cases function as a heat sink.

[Erkki]

It also can happen with caseless ammunition. It's one of the main reasons caseless ammunition isn't used much.

Similar to cased, only when chambered.

FN's SCAR rifle had a prototype variant with electronics that would change the rifle from closed bolt to open bolt mode if the temperature in the chamber got too high. No idea about how reliably or well that worked.

[AzyWng]

How do closed-bolt systems and open-bolt systems differ?

I know that access to air is affected (hence why cooking off is slower/not possible with open-bolt), but what else is affected? Production cost and time? Fire rate? Reliability?

[Strife26]

Yes.


In a closed bolt weapon that is ready to fire, there is a live round in the chamber, with the trigger activating the primer in some manner. With an open bolt, pulling the trigger is going to feed a round into the chamber, close the bolt, fire, and open the bolt again.

Very generally, open bolt is less expensive to produce and better for cooling while closed bolt has benefits with accuracy and reliability.

[Erkki]

How do closed-bolt systems and open-bolt systems differ?

I know that access to air is affected (hence why cooking off is slower/not possible with open-bolt), but what else is affected? Production cost and time? Fire rate? Reliability?

In a closed bolt gun, before firing the bolt is closed and has chambered a cartridge. Pulling the trigger then releases the spring and firing pin within the bolt, and the nail hits the primer and fires the cartridge.

In an open bolt gun, the bolt is locked back. Upon pulling the trigger, the bolt will be released, it will grab a cartridge from magazine or belt, chamber it and immediately fire. Gases or blowback system will then push the bolt back.

Open bolt guns cool down considerably better, can be belt fed and are slightly safer(more cook-off proof and once you remove the magazine its always clear). The downside is that because of the moving masses the gun shakes a bit before firing, effecting accuracy, and if the mechanism that locks the bolt back fails the gun will keep firing until it runs out of ammo. Also legally open bolt weapons tend to be "full auto" with very few exceptions even in the US. Typical open bolt guns are older submachine guns and almost all machine guns.

[Erkki]

https://www.youtube.com/watch?v=h5fvqmN578U

Thats a nice demonstrating video.

[Aseaheru]

 Closed bolt weapons can also be belt-fed, but many are openbolt for heat management and(to a lesser extent) ease of loading. Open bolt designs are also much, much easier to produce.
 There is some argument about which is safer, since you can have a closed-bolt weapon loaded but without a round in the chamber, but in heat management open bolt is safer, yeah.

 Also, in the US all open bolt weapons made after 1982 are classed as automatic weapons, period. Offically, this is due to the fact that they can be readily converted to being full auto.

[Akura]

Another good demonstration of an open-bolt weapon.

[TheBiggerFish]

Cook-off = heat up to the point where the propellant ignites by itself, right?

Yes. This is generally only a thing that happens in closed-bolt machine guns and large-bore weapons, although it's possible for it to happen with pretty much any bullet that gets hot enough. Protip: don't throw bullets into campfires.

Well, throwing bullets into campfires shouldn't do all too much?  It's not like there's a lot of gunpowder and there's lots of ways for the force to go...  I mean, don't anyway, but yeah.

[Strife26]

Cook-off = heat up to the point where the propellant ignites by itself, right?

Yes. This is generally only a thing that happens in closed-bolt machine guns and large-bore weapons, although it's possible for it to happen with pretty much any bullet that gets hot enough. Protip: don't throw bullets into campfires.

Well, throwing bullets into campfires shouldn't do all too much?  It's not like there's a lot of gunpowder and there's lots of ways for the force to go...  I mean, don't anyway, but yeah.

Yeah, it's not *likely* to do anything, but shrapnel and poor luck do unpleasant things.