I run a 16 inch Armson barrel on my H7 and it shoots great with paint. I am still not sold on fs rounds I have put over 50 thru the gun with only one kill.
Today I ran an Armson SSR, this is a straight rifled barrel from Armson it shot paintballs great but didn't shoot fs any better or worse then the spiral rifling.
One of the problems with fs rounds is they are not as consistent as people think. bore sizes change from round to round in the same box and the fins are not always clean, with bits of extra plastic to catch the wind. I had to file the tips of the round smooth because they can catch in the mags. the rounds dont break on body shots and if they do they don't leave a mark. even my one kill shot was a break that left no paint on the guys back, he called out from the pain. I found the broken round on the ground but he was clean.
they are fun to shoot because when they wizz by people they make a scary noise.