What kind of jam is this?

[commando552]

Thanks. I was hoping that it had a nice snappy name like "partial feed", or something like that. I vaguely remember being taught that it was called a "failure to close" but can't really remember. "Failure to return to battery" is a bit long winded (as well as seeming pretty vague to me, as that could mean that the slide is anywhere between fully back and full forward, by any cause).

Also, is this type of jam relatively rare in live firing guns, as I don't recall it ever actually happening to me without deliberately doing it by riding the bolt/slide forward. However I keep my guns pretty clean and am an obsessive "forward assister" due to being taught on the SA80 platform where it is part of the loading and stoppage drills.