A detailed question is the next. It is not specifically about WW2. It is about firearms and freezing gun oil in general. Whether it is possible even today to have a malfunctioning gun which was oiled, due to frozen (or more viscous) gun oil.
In Russian-language historical literature and popular talks I've encountered many times claims that the German Army and its allies experienced many problems related to the cold weather during the WW2, especially in the winter of 1941-42. One of these problems was that their gun oil froze, so that their hand-held guns, machine guns, aircraft guns (like MG-151) were not operational, so that they had to make bonfires to thaw them.
I'm rather skeptical about those claims about the gun oil:
- Guns have oil in a very thin layer to prevent corrosion, not to reduce friction. There is too little oil in a gun to freeze.
- While guns without oil can accumulate a considerable amount of frost in the right conditions, that frost is pretty likely to impede the use of the gun. A gun with oil shouldn't gather the frost, so the oil actually should prevent freezing.
- With padlocks, doping them with oil prevents freezing.
Can gun oil freeze in guns and prevent the guns from firing successfully?
A note: these claims are widespread is the Russian-speaking community of history-fans, so the list of references I'm providing here are not exhaustive, some of them are originally in English:
- the link to War on the Eastern Front: The German Soldier in Russia 1941-1945 The first paragraph and the next ones state:
When the first really low temperatures were recorded during the winter of 1941, the Quartermaster's Department of the Army was inundated with urgent demands for grease, oil and lubricants with cold-resistant properties. Units needed these special supplies to keep vehicles and guns in action, for the lubricants on general issue were found to be ineffective in the cold of the Russian winter.
The German Army made recourse to ad hoc methods. It was found that to prevent the action of rifles and machine guns from freezing solid every trace of oil and grease had to be removed. ... Corps and divisions fighting in the Ukraine and in southern Russia were less severely affected than those on the central or northern fronts and used sunflower seed oil in place of the standard German Army rifle oil.
Cold affected the large metal areas of armoured fighting vehicles and guns
This blog post in Russian tells a story about a scientist in St. Petersburg (then Leningrad) who found that German aircraft gas froze at temperatures below -14° Celsius. Lots of comments below tell "facts" that "ordinary oil gun perfectly freeze", "lubricant exposed to frost becomes more viscous .. and I've read memoirs of one German, who told how they learned from a Soviet POW why Soviet machine guns do not malfunction at the frost ..." and so on.
this book in Russian, The Tank Ram, says in the first paragraph on the provided page:
Today, January 8th 1942, the frost exacerbated even further. German soldiers were freezing. ... Gun oil was freezing in rifles and machine guns, in cannons. It reached the point that the Germans cleansed their arms but did not lubricate it. Such barbaric treatment of German arms did not passed without a payoff. Even extremely reliable Mauser carbines broke and jammed.
The original text, just for reference:
Сегодня, 8 января 1942 года мороз еще больше усилился. Немецкие солдаты замерзали. ... Замерзала оружейная смазка в винтовках и пулеметах, в орудиях. Дошло до того, что немцы свое оружие после боя чистили, но не смазывали. Такое варварство по отношению к немецкому оружию тоже даром не проходило. Даже сверхнадежные карабины маузера ломались и заклинивали.