First I looked at the relative momentum (mv) of a 2mm raindrop falling at 5 m/s vs a .177 Monster pellet travelling at 243 m/s (800fps = HV). Without getting into calculation details, the raindrop has about 1/10,000 as much momentum as the pellet.
Another approach attributes to Mike's observation of a puff of water vapor when a drop is struck by a pellet: the temperature (kinetic energy) of the water must be increased by the impact, from ambient temperature to approximately boiling temperature, in order to change phase from liquid to gas. Raising the temperature of 1cm^3 of water one degree C is the definition of a calorie - which is also 4.18 Joule. Without showing calculations, raising the temperature of a 2mm raindrop by 80*C lowers the energy of the pellet by 1 or 2% - which is well below typical velocity ES.
There are other calculations which can be done to analyze raindrop effects on pellet rotation speed, Magnus effect, etc. However the solution involves none of these, nor momentum nor thermodynamics. The actual solution is that one should never shoot in the rain because it will damage your wind flags.
Another approach attributes to Mike's observation of a puff of water vapor when a drop is struck by a pellet: the temperature (kinetic energy) of the water must be increased by the impact, from ambient temperature to approximately boiling temperature, in order to change phase from liquid to gas. Raising the temperature of 1cm^3 of water one degree C is the definition of a calorie - which is also 4.18 Joule. Without showing calculations, raising the temperature of a 2mm raindrop by 80*C lowers the energy of the pellet by 1 or 2% - which is well below typical velocity ES.
There are other calculations which can be done to analyze raindrop effects on pellet rotation speed, Magnus effect, etc. However the solution involves none of these, nor momentum nor thermodynamics. The actual solution is that one should never shoot in the rain because it will damage your wind flags.
