Barrel upgrade G&P spec ops

[Reaperman]

Afternoon,

Looking to get a bit more accuracy and range on my main as above. I believe she comes with a brass 6.05mm barrel and I have changed a few key bits with middling results so thought I'd try the barrel.

Can't seem to find the Prometheus one anywhere for sale, are they like rocking horse s**t? Need a 6.03, 300mm one I think.

Following the above, would anyone recommend the madbull one? Looks like they'll fit my gun.