The expression is very heavily used for one that is non-accepted, don't you think?
Does not make it correct or proper though. Does make the folks using it though seem immature - YMMV. Maybe having taught school for a while makes me dislike certain slang words, especially when one more key stroke allows the proper term to be used.
For many years a certain word used to describe persons of color was regularly and routinely used, even in the newspaper - didn't make it proper and correct, did it?
Back on topic.........while the KSG seems like a interesting application, I still wonder about handling with fully loaded magazines