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Old 02-21-2013, 01:31 AM   #1
Green-Neck
 
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Default [HT] Arctic cold and guns

I'm currently preparing for a session where my 5 rocketeer players are arriving in 1938 Spitsburgen [Svalbad]. I'm wondering what effect cold will have on their myriad firearms. I'm setting the local temperature at -25 C [-13 f].

I would like some help developing some easy rules devised from an article named Firearm Maintenance and Precautions for Cold Weather, by Adam S. Gubar [or other sources people may be able to link to].

It appears from the first paragraph that misfires in pre percussion cap rifles were over 30% in very cold weather. For a TL5 firearm [malf 15?] that requires -3 or -4 to get to malf 11-12 [30ish%].
I wonder if there is a graceful way to scale cold weather induced Malf at different temperatures.

The article cites a 2:3 ratio for temperature below 0C, every 2 deg below lowers the effective range by 3% due to denser air. At -25 C we have 37.5% reduced effective range. I'm thinking that’s close enough to say -1/3 half damage and maximum range – or am I over simplifying the physics?
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Old 02-21-2013, 06:55 AM   #2
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Default Re: [HT] Arctic cold and guns

I'm not a gun geek, but from time to time I do translate operator manuals for a major small-arms manufacturer. The recommendations in that link are in line with what that manufacturer recommends. If it were me, I would prefer to use a low-temperature oil rated for whatever temperature it was, but test it myself anyway.
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Old 02-21-2013, 08:53 AM   #3
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Default Re: [HT] Arctic cold and guns

There is an existing thread on this which you will probably want to read. I think the Canadian Rangers were mentioned in it.
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Old 02-21-2013, 08:59 AM   #4
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Default Re: [HT] Arctic cold and guns

I don't know much about it personally but have just been reading Chaosium's "Beyond the Mountains of Madness" book (link) in preparation for a (far) future CoC campaign. It seems well researched and contains lots of details on arctic cold effects on people and equipment.

I don't have clear recall on what it said about guns but it sticks with me that they won't fire at all below a certain temp and that the suggestion was that the PCs keep them within their clothing. Maybe the oil would freeze or something. Of course, this is set in the 1920s so may not be of much use to you...modern adventurers may well be able to take advantage of some advancements that have come along since then.
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Old 02-21-2013, 09:08 AM   #5
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Default Re: [HT] Arctic cold and guns

Quote:
Originally Posted by Polydamas View Post
There is an existing thread on this which you will probably want to read. I think the Canadian Rangers were mentioned in it.
The Danish "Sirius Patrol" troopers, who patrol northern Greenland during the local winter, use some ancient tech rifles, probably TL6, exactly because those are known to fire reliably even in extremeley cold weather. It's so they can defend themselves against polar bears.
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Old 02-21-2013, 11:38 AM   #6
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Default Re: [HT] Arctic cold and guns

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Originally Posted by mearrin69 View Post
Maybe the oil would freeze or something.
Many oils and greases thicken at low temperatures and loose their lubricity. This is disastrous for most self loading small arms.

Their are of course cold resistant lubricants intended for firearms in the coldest possible temperatures like LAW and TW25B.
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Old 02-21-2013, 05:56 PM   #7
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Default Re: [HT] Arctic cold and guns

ok- guns and extreme cold:

#1- gas blowback will not work on automatic fire (unless there is a gas regulator available that can be altered for cold temperatures). Semi-automatic gas blowback fire will still work, but see below.

#2- oil is too damned thick, if your not using a cold rated oil (which will likely actually be a suspension of tiny graphite beads or silicone beads in alcohol), the gun will probably not fire the first time, and will have a lot of misfires until suitably warm, but see below.

#3- condensation sucks, and will plague you. Every shot fired will heat the weapon, further the hydrocarbons in the powder burning will release a lot of water vapour, which will then condense on the (comparatively cooler) metal due to the extreme cold. This will introduce moisture in all parts of the mechanism which deal with the ammunition, and these will interract poorly with the low temperature oils and see below.

#4- once fired you need to get it clean and dry FAST. Once your done firing that weapon needs to be dry cleaned almost immediately, preferably in a warm place, because all that water vapour is going to freeze on it unless it stays warm (which it got because of the heat transfer from firing). If ice develops in the mechanism like on the firing pin, it will not fire, or cycle rounds. If enough ice develops in the barrel the weapon could explode when fired.
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Old 02-21-2013, 06:06 PM   #8
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Default Re: [HT] Arctic cold and guns

This is all interesting stuff for a hypothetical alien species on a cold world.
Could they develop workable guns without first inventing the warm working ones?
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Old 02-21-2013, 06:43 PM   #9
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Default Re: [HT] Arctic cold and guns

Quote:
Originally Posted by starslayer View Post
ok- guns and extreme cold:

#1- gas blowback will not work on automatic fire (unless there is a gas regulator available that can be altered for cold temperatures). Semi-automatic gas blowback fire will still work, but see below.
Gas and Blowback are two different operating principles.

Gas operated rifles have been chugging along merrily in arctic conditions for nearly a century.

Quote:
Originally Posted by starslayer View Post
#2- oil is too damned thick, if your not using a cold rated oil (which will likely actually be a suspension of tiny graphite beads or silicone beads in alcohol), the gun will probably not fire the first time, and will have a lot of misfires until suitably warm, but see below.
Uhhh..No. Just..no.

Quote:
Originally Posted by starslayer View Post
Every shot fired will heat the weapon, further the hydrocarbons in the powder burning will release a lot of water vapour, which will then condense on the (comparatively cooler) metal due to the extreme cold.
Hydrocarbons are a waste product of the combustion of Nitro powders. There isn't enough (really any) free water formed to be of concern.
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Old 02-21-2013, 07:32 PM   #10
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Default Re: [HT] Arctic cold and guns

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Originally Posted by Sam Cade View Post
Gas and Blowback are two different operating principles.

Gas operated rifles have been chugging along merrily in arctic conditions for nearly a century.
Gas blowback pistols, rifles, and machine guns are a thing, they hate the cold. Nothing I have said here is incorrect, I mention them because of the time period the OP suggested (Though on double-checking the gas-blowback weapons on wikpeida they are all too late in period to matter)

http://en.wikipedia.org/wiki/Blowbac...s)#Gas_delayed

Quote:
Originally Posted by Sam Cade View Post
Uhhh..No. Just..no.
http://www.mil-comm.com/index.php?op...d=29&Itemid=43

The site for TW25B describes it as tiny beads of ptfe suspended in a carrier grease, I'm not sure what you find incorrect about the mechanism of one of the very oils you cited earlier as being used in cold weather.

Quote:
Originally Posted by Sam Cade View Post
Hydrocarbons are a waste product of the combustion of Nitro powders. There isn't enough (really any) free water formed to be of concern.
Unfortunately a quick google search did not turn over data on this one for me to refute your statements with, so I will drop this point. Regardless of where the moisure comes from (casual condensation from the cooling of metal that was heated up, or provided by the combustion process)- that moisture/ice is disastrous and will need to be dealt with.
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