It's definitely a liquid CO2 issue as sometimes the velocity spikes mile-high as well when cranking out suppressing fire. It's a tempermental old thing, sometimes it's as consistent as a top-dollar reg setup and sometimes it's a nightmare. I've put up with it for ages but I'm getting bloody sick of it now.
Guess I'll remount the ASA under the body to turn the bottle vertical and see how that goes. Just a matter of figuring out how to attach a piece of material to put it there, besides using a plumbing clamp.
It's going to be a challenge as there's really no place to tap and mount it on the body and I wouldn't trust the plastic in the front part of the trigger mould to hold together if I yelled at it, let alone mounting the bottle there. Mounting the ASA on the plastic itself is a recipe for disaster -- one bad slide and I'd have a bottle rocket spraying boiling CO2 at my crotch.
Perhaps I could make a thin bracket that could go between the grip and the body, held in place by the front grip screw? I'd be restricted to using bottles short enough that they don't dip below the bottom of the grip, but I know where I can track down a couple 3.5 ouncers. I'd have to reinforce it with another screw horizontally through the plastic to give it two anchor points in case it's hit from the front and risks stripping the front screw.
Guess I've got a project and a reason to pull my digital camera out of storage now. Any tinkerers more seasoned than me care to dispense some advice on the matter?
EDIT: Or perhaps I could just do this.
Typical. My gears start rolling and then I discover that someone else has already solved it and done a better job than I could have.