The gun was a Scaramanga Special, as shown by the earlier scene where it was being assembled. It was probably only a single-shot gun.
It actually had two. He used one on Claire, and the second goes off while he was fighting with Ethan.
Fridge Logic: At the end of Ghost Protocol, why didn't the new iPhones that Ethan handed to his team self-destruct? I thought all mission briefings did that...
They hadn't listen to the mission statements by the time the credit rolled.
In Ghost Protocol, why didn't Hendricks toss the suitcase off the ledge and keep fighting Hunt to buy time?
I assume he was protecting it with his body, so it wouldn't be too damaged to work.
He was beat up pretty badly at the time as well, he might not have been thinking clearly.
Fridge Horror: In the first movie, Secretary Kittridge sent Hunt's IMF team to retrieve a stolen list of Code Namesas part of an internal "mole hunt" - and was completely unsurprised when Hunt was the Sole Survivor, whom he thus believed to be the mole. He effectively sacrificed the entire team to catch a single mole. The whole "disavow any knowledge" meant the loyal team members were expecting to stake their lives on their talents without a net, but sending them on a Suicide Mission without their knowledge? Granted, he was really pissed off afterwards at the deaths and there was really no other way to expose the mole, but dude, that's cold. Justified, but cold.
Perhaps he wasn't expecting the mole to reveal him/herself by killing the rest of the team, but when he got the news that they all were dead, figured out quickly that this would expose the mole anyway.
Additional thought on this: Kittridge did have thew other team to watch it was going on, his plan was likely that the mole would reveal him/herself by some actions that the other team would spot, but expected this to be done in a more sneaky way. However, Kittridge throughout the movie is shown to not react all that strongly to anything that happens, even things like seeing Jim alive, so it is likely that he wouldn't react to strongly to the team's deaths either, and that he would quickly figure out that Ethan was apparently a likely mole.
It's not cold, it's intelligent. If the NOC list gets out in the open, hundreds or thousands of agents across the entire world (not to mention their friends and families) are at extreme risk of death. Putting the lives of a few agents (who risk their lives on any mission in the first place) is small potatoes considering the greater good.
Fridge Horror / Fridge Logic: In the second movie, Ambrose's plan is to allow Nyah to walk around after she's infected, but Nyah decides to simply kill herself after 20 hours rather than get infected. If the disease is contagious before the 20 hours, how did all the other people who may have gotten chimera get treated? (Presumably biocyte could have done it, but it would seem a bit strange to have biocyte make some extra money in that way after their part in the situation) If the disease is not contagious before the 20 hours, how did Ambrose (who seems pretty smart at that sort of thing) not think of, or otherwise plan for, the possibler suicide happening?
Fridge Brilliance: (or fridge humor, if it was an article) Venus is an even more appropriate name for Carter in Ghost Protocol than you might think at first. It is a planet thought to look beautiful, until people got a closer look/got through the clouds, than it became deadly.