It does my heart good to see a quality firearms discussion in a fact-checking thread!
So many books do a terrible job with guns. I'll extend my irritation to gun play and fighting in general. There are right and wrong ways to handle a firearm, and right and wrong ways to fight unarmed.
Here are things I wish action writers would do a better job with:
-There is a difference to how trained soldiers and operators handle a gun fight and how gangsters and criminals do it. A lot of great action scenes can be built off of this. Lots of tier one units get surprised by scrappy opposition with a good plan and decent training, let the differences shine and you'll get a great conflict..
-Fistfights look very different than how most people imagine them. They are shorter, less graceful, and gorier than you think. Watch some Worldstar videos and fights caught on security cameras. Focus on what happens when untrained people fight with well-trained people from full-contact styles (boxing, judo, jiujitsu, wrestling, "MMA" etc.) The differences in how they move and fight are huge.
-Just because a guy was a SeAL (SAS, Ranger, whatever) does not mean he's a great hand-to-hand fighter. Hand-to-hand is pretty much obsolete in modern warfare, and even the most elite units spend only a little bit of time on it. As they should. We have guns, and specialists are very good with them. We shoot bad guys, not punch them. However, the average special operator is going to be in MUCH better physical condition than most of the people he/she will encounter. That can make for a very interesting fight scene.
-Learn the difference between "concealment" and "cover." If the bad guy has a .44 magnum loaded with buffalo bore 310-grain hardball, that restaurant tabletop is not cover! Conversely, if the good guy has a Ruger LCP in 380, the bad guy can hide behind whatever he wants. The Lee-Enflied discussed earlier will shoot through pretty much anything a person is likely to find for indoor cover. But no one is really going to use a LE indoors, anyway.
-Guns are loud. If your hero shoots a gun indoor without ear protection, your hero is going to be deaf in the closest ear for several minutes. If the gunfight drags on, tinnitus is part of his life for a while. This can be inconvenient for storytelling purposes, so I usually let this one slide.
I'm sure ther are more, but these are the ones that get my goat when i read and I try to avoid in my writing.