Two things about modifications. 1, if the guns are allowed to cool to ambient temperature, there's going to be some metallurgy problems. Ignition parts
work by striking stuff; the shock loadings slightly deform firing pins and hammers and whatnot over time, but at very low temperature the normal metals used
are likely to start chipping from brittle fracture, or possible breaking more severely. On the other hand, with heat transfer to the (admittedly very cold)
environment being only through radiation, repeated firing is going to make things get very hot. I don't feel like doing math on it; suffice to say that
even semi-automatic weapons may run into issues if used enthusiastically, and machine guns would either have to use superalloy barrels setup for quick changes,
or be cooled with a heat exchanger (ala WW1 water cooled guns).
work by striking stuff; the shock loadings slightly deform firing pins and hammers and whatnot over time, but at very low temperature the normal metals used
are likely to start chipping from brittle fracture, or possible breaking more severely. On the other hand, with heat transfer to the (admittedly very cold)
environment being only through radiation, repeated firing is going to make things get very hot. I don't feel like doing math on it; suffice to say that
even semi-automatic weapons may run into issues if used enthusiastically, and machine guns would either have to use superalloy barrels setup for quick changes,
or be cooled with a heat exchanger (ala WW1 water cooled guns).