Do you have a manual ? There you can see what comes in which position:
How old is your A5 ? (Cause the diagram is from the newst A5)
Did you screwed on your velocity set screw ? (Should be in max. position if you look without the barrel in front of your A5 inside the bolt you see the screw if not itīs allready set max. fps)
Mmhhh you polished it should be better than stock !!! May if cocking doesnīt go smoth your framescrews are screwed to strong !?!? Stockspring should be good for over 300fps !!!
The Flantlinebarrel has a very big bore so you lose alot fps by using him, you should have min. 260fps !!!
I got a old Antiliquid without internals as Voluminizer which gives you alot more fps if nothing else will work: