I agree. I just said 'decent idea' -- thinking average joe not 'what the developers should do. By all means, they should strive to use real recordings as much as possible.
Knowing what low-quality recordings will do to sounds, you can formulate a decent 'guess' [as an average joe, not a develper] as to what a real gun sounds like. Especially with more common guns like M16/AR-15, AK, mp5, m9/glock, there are numerous vidoes to judge the differences from one recording to the next, either in the same type of setting or different. It's interesting to note how intimidating the sounds are in a non-insulated indoor gun range vs. out in the open and even the covered outdoor ranges.
In general, guns are so much louder relative to other sounds that their realistic modelling and in-game implementation is tricky in the least. We can only hope in GB that the developers get some good 'trigger time' and do their best that the sounds replicate what they experienced.