Perhaps I wasn't clear. Bufferless rifles like the FM15 require no assembly. Since they have no buffer, they can have a brace or stock that folds, making the entire weapon barely longer than an AR upper alone. That's why I contrasted them:"Barely more time" is a lot of time when comparing how long it would take to get any kind of "pack rifle" unlimbered, assembled and ready to go as opposed to drawing a handgun from a holster.
AR15 pistols.. work great, as long as members have the time to pull out the receivers and assemble them.