Tightening the barrel jam

[vernongt]

G'day Airgunners,
I am curious if there is a way to tighten the barrel jam on my Hatsan 125 Black NP 22 rifle.

I have installed a GrovTec QD sling set, the barrel band is just about 1/2" from the barrel block, but I've managed to break the barrel open while having the sling over my shoulder.
I'm sure someone is gonna tell me to put the top sling swivel at the stock bolt [on the side] but I don't wanna do that!!! 

The barrel jam holds the breech seal close to the Compression Tube outlet, but the jam spring seems to be a little soft.