Nate I've had my Airmax Dominator since the SPAM16 first hit the airgun market. Mine is .22 and I simply love it, it's the most accurate PCP that I own, the barrels on the .22's are known to be extremely accurate. That stainless piece that you were pointing out is actually the barrel connector and it has the transfer port in it. I even ordered a couple extra of those direct from SPA along with 2 extra clips, gauges and a spare regulator for about $100 shipped
Right now I have mine tuned for 4 clips worth of my 23 grain cast Magnum Hunters that are really excellent, they're good and accurate doing 35fpe and will really reach out there. Like I said it's my favorite PCP for hunting and I'm having fun making the ammo for it as well.
I took this picture in early spring of 2018 (Notice my gun leaning against the trailer), the guy that owned the John Deere has since sold it and bought another bulldozer. I think the John Deere is a 1958. I sure did get a charge out of watching this old creeper running, it's a 2 cylinder and really sounds neat. I talked with a friend of his recently who informed me that he sold it that also had fun running the creeper as well.
I might also add that the German Beech stock that comes on these is extremely tough, I've put mine through holy H and it still looks really nice, whatever kind of finish the Chinese put on these guns it's extremely good and made to be used and used more.