Randy Thom 
It's extremely unlikely that any dialog recorded while a gun is being shot will wind up in the film when it's released. Those lines will almost certainly be ADR. Even if you do an excellent job of avoiding distortion from the muzzle blast while still being able to hear the dialog, the sound of the gunshot is very unlikely to be ideal. Blanks don't sound like real bullets. The acoustics of the place you are shooting in are likely to be less than ideal as well, and the gunshot will tend to describe the acoustic space it is in even more than the dialog will. 

So, if you want your production sound to make it into the film you should lobby heavily to do wild lines on the set immediately after each set-up is finished, while the actors still have the right kind of energy. Also beg them to avoid off-screen gunshots at all times. That'll give you a better chance to get something useable while the camera is rolling. 

I would insist on knowing exactly when each gun was to be fired. That will help to protect your ears and your track. Limiters wouldn't be a bad idea whenever a gun is going to be shot. Somewhere between 10 and 20dB of padding should be enough, depending on the gun, your distance from it, the acoustics of the place, your pre-amp, etc. You might want to use dynamic mics rather than condensers. 

Obviously, you should request a rehearsal so that you can get in the right ballpark gain-wise and in terms of mic placement before you're expected to have any chance of getting a useable recording when the camera is rolling. 

When recording both gun shots and dialogue, I never use a limiter or compressor on the mic channel as it may well not recover in time for dialogue. At the same time I turn the headphone amp down to zero(must have a control that fully turns this off-no leakage allowed) and turn it back up for the lines. As Randy indicated, rehearsals are a must.   Also, do not use Sennheiser 416's as they have been known to die in these situations (anecdotal evidence only). I use Schoeps and Neumanns. They bottom out on the initial shock wave but usually recover in time for the dialogue.