Wind angle could be 0 degrees if wind is coming straight from behind, and 180 degrees if it's coming straight from the front. It could also be the other way around :P
The bullet coefficient is probably the 'ballistic coefficent'. It's probably specified to bullets, using the g1 model.
Here's a list of commercial BC's: www.frfrogspad.com/g1bclist.xls
Here's a list of militairy BC's: www.frfrogspad.com/g7bclist.xls
The commercial one uses the g1 model, which is old. But since your apps are coming from weapons manufacturers it's likely they use the G1 model.
With a higher BC, a bullet will lose less velocity. The manufacturers use this old G1 model so they can tell people their bullets are awsome, which they are not. In the commercial list there are bullets which have a BC of higher than 1.0. This means you're actually firing a laser canon.
I hope this helps.