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I am curious what would happen if somebody tried to fire a firearm in liquid nitrogen?
I assume that if the bullet is soaked, it just will not fire.
Otherwise, would the gun just shatter? What do you thing the projectile would do?

The gun itself should be okay, as long as one did not attempt rapid fire, you'd need some slow shots to warm it back up. We already have weapons rated for automatic fire at -40 C as it is. -200 C is a lot colder, but that goes back to fire single shots. The Russians made a 23mm automatic cannon work in space and it was in orbit more then long enough to cold soak, but it may have had a heater and I assume it was getting some solar heating. The big cold problem with guns is the lubrication freezes, that could jam any weapon, but you need lubrication far less if the gun is cold!

If it did fail it would fail at the locking lugs of the bolt. Other parts might crack microscopically (this could get worse fast) and the springs in the action will hate life, but the weapon just coming apart into a bunch of pieces doesn't seem likely. Maybe if you got it way colder?

As for the ammo, yeah I think it wont function because the primer will freeze up too much, but a quick search of the internet turns up no useful freezing data for any common primer material. If it did fire then the propellent would be cold enough to have a significant reduction in muzzle velocity. Some propellents now exist which are temperature insensitive over normal military operating ranges, but nobody is using that for small arms, and I doubt they are actually insensitive to such an extreme as this.

Kind of on a spotty mobile broadband at the moment. . . Not a great signal.
Thought I remember seeing a video once of a hammer soaked in liquid nitrogen and shattered.

well if anyone has a good chemistry book around, a lot of primers are Lead Azide and Copper Azide together these days, the sensitivity of said compound would be decisive. If the primer detonates I doubt the powder will be cold enough to fail to ignite.

if somebody tried to fire a firearm in liquid nitrogen?

They'd freeze!

Kitsune wrote: Thought I remember seeing a video once of a hammer soaked in liquid nitrogen and shattered.

Could be, but tool steels tend to be low quality and very hard as opposed to very tough with only a basic heat treatment. They'd crack up being used in a firearm at room temperature. The gun might well crack up, but I really don't think that's a given. Reasons exist why a good hammer is 30 dollars and a good serviceable handgun is 600-800 dollars or more, though higher prices usually involve low production runs. Or things made by Germans.

At first, you'd ruin your hand by grabbing it. Even a glove would not help you as anything thin enough to let your finger still reach the trigger will probably not help your hand survive inside the nitrogen.

I'd guess that the gun won't fire (properly) - the lubricant and moisture residue would probably freeze the bolt locked. It might be tight enough to make it jam or fail to ignite the primer. And I'd expect hang-fires. If the primer actually still works at that temperature - cooling down is one thing done to keep explosives from doing their thing.

If it were to fire - it would probably crack the action or the barrel - you are firing it inside a liquid, which means that the higher bullet resistance would put more pressure on the gun itself, which is currently weakened by the cold, already.

The fact that the igniting bullet will also instantly vaporize all the liquid nitrogen that comes in contact with the heat (means: inside the action & around the barrel) will make this even worse, I'd guess.

You could use a tool to fire it. Thing is just about any heat at all will make a large amount of liquid nitrogen boil back to gas, so it'd only be possible to fire it in the liquid if you'd also chilled down the firing tools and insulated them, so I kinda ignored the 'fire inside' bit, because most likely it wont be liquid a the point of firing. Its actually really crappy at being a coolant, its just readily available, very safe when it boils and above all cheap for giving demonstrations.