Hi I have both and I find the FSB without a silencer is louder than the standard with silencer but add a silencer to the FSB and they are both very quiet must admit I love the FSB carbine .Regarding the A & M cylinder I wanted to fit the full length one to my carbine fsb but it would have been tight on the silencer so spoke to A&M and they have made me a custom length of 300 mm looks great .is lighter so better handling and shot count in .177 is 105 shots before drop in poi from 200 bar fill I believe they are now carrying this as a stock length for the FSB .I havnt had the chance to check the shot count in .22 yet hoping to get that done tomorrow.
Regards Steve