[tunabreath]

Yeah. All the important ones are for the CA870, which (as I've gathered from reading about them) is mostly incompatible with the M870/M1100 series. The M gas powered ones use shells fed from the tube magazine, while the C spring powered one has a detachable box.

But if anyone could point out exactly what is compatible and what isn't, I'd be quite grateful. The details I'm looking for most are the hopup/inner barrel mounting system, and the magazine tube mounting system/dimensions.

I also wonder if the nice collapsible CA870 stock there can be modified in any way to either accept the original M870/1100 grip and gas components, or at the very least, have an external gas supply routed through it.