My tolerance for bad storytelling is pretty high in my opinion, and this manga is such a bad experience for me that I can't even bring myself to recommend it.
Predictable, uninteresting and dull.
The only thing going for it is probably the relationship between the two main characters, but for me, it was not even remotely interesting due to it's predictable progression.
The only fortunate thing I can say after reading this manga (over the span of a few years, due to me refusing to buy the manga, (but able to read because my housemate is a big fan of girls with guns) is that it is NOT LENGTHY.
Heck, it even takes me about a week to even finish one volume because it was not appealing to me.
Still, I do think that it would have held promise if the characters were fleshed out better, but that is not the case in this manga for me.
Still, for manga readers who like girls with guns, can't go wrong with this one, but for people with eclectic tastes, this is probably a manga you'd regret NOT reading.