[L473ncy]

Sorry, no knowledge about the G&P WOC GBBR however gasguns.info is a resource that you should take a look at, basically to my understanding it's like the "SystemA PTW Owners forum" with a plethora of resources that are available to you as well as in depth discussions and a large knowledgebase.

In short, go there for all you need or ever want to know about GBBR's.

Oh yes, the ICS also does have a sort of "quick swap" upper and lower so that's an option too, don't know why I didn't think of that at all I guess it was just a mindfart or something.

As well I believe the STAR/ARES line of guns have a "quick swap spring" feature or something but you'll have to do some research about that on your own that's all I know about it.

EDIT: Also, yes I do know that AEG's can sound like "sewing machines" but you can reduce the noise by doing a few things like sorbo pads, correct motorheight and helical gears but it will never be eliminated I guess you don't get that with the GBBR though since it's operated by gas rather than a motor.