I am one thoroughly confused airsoft player.
So, I normally run with the stock (soft) hop sleeve because the prometheus hard sleeve was way too tight on my stock inner barrel. Naturally when I changed over the barrels I put the stock sleeve on my new one, just on auto pilot I guess.
However, I'm so sure I swapped out the hop sleeves before posting this thread - it's like one of the first things to test with this sort of problem in my eyes. In any case, I just swapped the soft sleeve for the hard sleeve (which as I was putting it on was a much snugger fit) and viola, back to 530 FPS...
I'm such a tool. Sorry to bother you all, and thanks for the replys that were given!
Problem solved
