Of course, he offered no explanation of how he came up with that number. 

Via Breitbart:

During a Q&A session with the Los Angeles Times, gun control proponent Micheal Bloomberg claimed the number of American gun deaths exceeds the entire history of American military deaths.

He offered no substantiation for this claim. Rather, he just interjected it into the dialogue, then moved on to the next point...

...Bloomberg claimed that roughly 31,000 Americans will be killed this year with “illegal handguns.” He offered no substantiation for this claim, but seems to be assuming that a gun legally purchased, then used in crime, is an “illegal” handgun. But he cannot support this claim. After all the effort and money he spent to be sure Americans must go through background checks in order to acquire guns, he cannot then call those guns “illegal” simply because empirical evidence shows background checks fail to stop determined attackers.

Bloomberg told the Times that the number of American gun deaths exceeds the entire history of American military deaths. He said, “There have been more people killed with illegal handguns than soldiers that have died since the Revolutionary War through today in defense of our country.” Again, he provided no substantiation for this claim. But it should be noted that the Center for American Progress Action Fund (CAP) made the same claim in 2015. The claim was wrong then and it is wrong now.

Read more here.