I don't have any first hand experience but I recently read some posts on a popular pro audio forum. Here's some of what they said. (I don't think I'm allowed to link directly to the forum so that's why I'm not just posting the link)
" Having done some gun recording, let me give you a few pieces of advice. First, and this is probably obvious, but, be aware of the very high SPLs. They can easily overload even a robust mic, leaving you with a poor sound. Second, an this is related to the first point, guns don't sound very good close-mic'd. Less like a BOOM! and more like one of those firecrackers you throw on the ground and give a small 'pop'. Last, handguns almost always sound wimpy. If you want ballsier sounds, I recommend you record a lot more bigger guns than you might think you need. Even higher calibre handguns sound more like firecrackers and less like glocks. There's a certain element of sound design that goes into doing a gunshot library; it goes beyond simply capturing the guns' raw, natural sound."
Here was another answer from Michael Wagener(Producer, engineer has worked with Extreme, Kings X, )
"It's very hard, if not impossible to record a gunshot outside with no reflections. I've tried a bunch of different guns, and a bunch of different mics (including Fritz the head, which goes down to 2Hz). What you are hearing in the movies most likely has been recorded with the reflections of an indoor shooting range or some kind of room. Outside you only get a quick dry "pop", maybe the sound is too fast for a mic/preamp, dunno. Shotguns have quite a big boom but a 44 magnum with a 240 grain (or higher) bullet does a fine job. Weird enough, I had the best results with a Video camera mic (and probably built in compressor) which brought out the reflections of the outside area nicely."
This is from charles maynes(worked on sound for Grindhouse, Call of Duty 2, Starship Troopers)
"Unless there seems to be a really good reason for it, I set my levels to basically go to audible distortion, and then back off. I do test recordings where I record a few shots and then review them. I have lately been LOVING the Sennheiser 416 about a meter from the ejection port of the weapon.
This is from charles maynes(worked on sound for Grindhouse, Call of Duty 2, Starship Troopers)
Dynamic mics like an SM57, 421/441 and PR40 will NOT give any tail to your recording. They will give a good, tight attack though-
For the tail, I usually go to the Oktava's which I will either set up as an XY pair or sometimes as spaced dual mono. I am also a behind and to the side of the weapon type guy- this just shows there are many equally interesting approaches to recording stuff like this.
As to placing the mics in front of the weapon, some mics do not mind it, some do- I am almost always putting a pair of SM57 out front, and the MXL-990's have worked out there too- at about 5 meters generally-
The other thing about going the multitrack route is much greater flexibility in post- you can make different perspectives and distances with a good assortment of angles."
