Does the inner barrel have an o-ring on it, towards the muzzle end? If not try finding one that will fit in there.

No, there's no o-ring, but i could go try to find one at a hardware store, like was previously mentioned. Probably don't wanna bring my whole gun there though!

Anyway CDN: without tape to partially stabilize it, it goes way off to the side at any range, but of course more noticeably at longer ranges. I fired at something at a range of about 30 feet or less like you said and it's off by a meter or 2. So that's really not good. With tape stabilizer, I can hit single cans (1 shot each at 3 cans = 3 hits) at about 4 or 5 meters.

So maybe I'll just have to stick with the tape, or try to find an o-ring.

yes i was thinking about sliding over the inner barrel from the front. if the tubing,fitted either snug or adhered onto the inner barrel, idea doesnt work im wondering if an o ring (previously mentione)slipped over the inner barrel would be enough to pick up the slack.

Fixed mine with oversized O-ring. If your inner barrel doesn't have a groove for the O-ring then file it.