RBG: Shotgun Style
Yes, it is the only shotgun rubber band gun that I know of. It is based off of the Remington M870 and can be easily modified to be both be in an entry shotgun configuration, with tactical buttstock, or in a "Breeching weapon" configuration, with no buttstock. In the first picture, it is in the entry configuration. In the second picture, it is in the breeching configuration, but with the buttstock shown to show how it could be carried in a briefcase or something similar. There is no difference whatsoever between the two, other than the obvious difference in the buttstock, but less obvious, the breeching configuration has more mobility in the cocking hammer, so it works better. I am sorry for the lack of pictures of the internals, I will hopefully be posting them in the future.