So is an sm81 the best choice to record gunshots?
 

Title says it all. I want to cleanly record gunshots. I'm also wondering if that level of percussion requires me to protect other mics.

As an example... let's say I'm shooting a scene in a house and we're using a blank gun to simulate a hit. Is my on-cam dvx mic gonna' suffer damage when that piercing "bang" hits it?

I have an m58 handheld eng mic that I think could get the gunshots, but I haven't seen any verification that it can and I haven't tested it yet. Also I have an mke2 red-dot which is a reduced sensitivity lav that I could employ.

Thoughts?

Cleanly recording them may not be what you actually want. Real gunshots are supremely harsh and unappealing.
I know you mean you want to record them without overload and distortion, but you will probably have to do some experimentation and separate recording and replacement to get the sound you want.
The SM81 is a very good mic, but there's two things about it I don't like. Its high cost and the attenuator ring that can only be locked by taking the grill off. It is normally very easy for it to slip away from the setting you want.
I think you could get equivalent results from an AT3031 which actually has a higher rated SPL and similar sonic characteristics. The AT has a hotter output though, so you might have to attenuate it before it goes into the mic input even if you already have the camera set to -50db. The 3031 is available for about $170 and has a very positive pad switch.
Your M58 doesnt have a listed SPL, but I imagine it could stand up to it pretty well as long as it was at least 10 feet away, especially outdoors. Indoors is another thing entirely for any mic.
Mixing two mic signals together, like one condenser and one dynamic may also get you closer to the sound you're after.
There are alot of dynamic mics you could try if you didnt want to risk your Beyer. AKG D770, D880, Sennheiser e835, EV 635, Shure SM57 or Beta57a, ATM-27, ATM-29, ATM-41.
You could wrap something like a folded handkerchief and rubber band around your built-in mic. This should protect it enough from the main impulse. It might even record a cool sounding shot depending on the indoor acoustics and the load used. Experimentation is the key.

The Sennheiser 421 is supposed to be the best at recording
gunshots as it can take a higher SPL (sound pressure level)
than any other mic (or so the legend says).

The 421 is an excellent dynamic and does a really good job
on everything from voice to drums to horns. The later models
have a variable low end filter.

Hmm. My 81C filter ring doesn't turn all that easily and if it did, a spot of gaffer tape would solve the problem.

Either unit should be fairly rugged.

Truth is the micorphone that came on my DSR-300 does almost as well. Some people almost throw those away!

The best recording I ever got of a gunshot was when one of my cameramen taped a SWAT exercise while he was sitting on the garage of a house under 'attack.' He was shooting with a handheld Sony PD-1 and allowing the onboard stereo microphone to record wild sound (we had the setup separately mic'd. Incredible sound. It also did very well with the Flash Bang Grenade they threw on the ground under him. He almost bounced off the garage but that's another story.