Vulcan problems

Okay so I bought a Vulcan from a friend and having a little trouble. The thing is accurate as hell at 6p yards but anything past that it looses it's accuracy. It's a .22 and it's was shooting at 930 fps and I thought that was a little hot for the 18.13 cause of the spiraling. I adjusted the reg to about 120 bar and now it's shooting around 880 and still spiraling. Not as bad but still is. I'm not sure what to really do cause when my buddy had it it was shooting great out to 100 yards and he changed nothing... Ernest Rowe tuned it and put in a smooth twist barrel when he had it... just need some thoughts on what to do with it.. my plan is to get it to shoot amazing again then sell it
 
He would shoot on cam in slow mo at 120 and no spiral at all. He sold it to me cause he bought a .25 impact and just didn't shoot it. He got it back from Ernest the same time as his impact and just let it sit around for awhile. It's accurate at every yardage until about 75 yrds. The group's open up the further out you go... I'm wondering if the jsb pellets I have are a little different or something. Anything with in 75 is down. But also sometimes at a further distance such 90 yards I'll get great groups and other times they are better than 3in at like 85 90 yards 
 
Try shooting without the shroud and compare groups with more then one kind of pellets.

I had some vulcan had turbulence issues with the shroud, being to tight, loose rear bushing, loosen center 1/2 20 bushing and all depend what type of shroud you have, I even enlarge the shroud bore hole so slightly and that made the difference.

i suggest testing shroud 1st before going further brain storming.