I purchased one of the last FWB Sport rifles AoA had, number 635 for those keeping track. Read everything I could find before purchase. Most complaints seemed from those echoing what they read/heard or just wanting to throw rocks, not often from those with personal experience. Found
@razor62 videos of journey from critical to loving the rifle very beneficial. Absolutely no regrets with this purchase, the Sport is a very fine rifle. My compare tos are my FWB 603 and AA Pro Sport.
I have opened mine up. Internals are not substandard by any means. Good materials, high quality machining fit and finish. Choice to use a loose guide was unfortunate and piston seal some found lacking, otherwise definitely up to standards I expected.
Initially exhibited definite twang, but that moderated significantly after 300 or so rounds. Calming down as gun breaks in.
That said at about 400 rounds I did replace the piston seal (mostly because this was a common criticism and I was curious) and applied tar to the spring guide. With those minor changes the shooting manners are quite pleasant, see no need for any extensive tuning, tune kits or further mods.
New Vortek piston seal made no difference in chrony numbers but did soften (buffer) end of piston stroke eliminating hard stop, so worth it for that. I assume difference is from concave face of Vortek seal. Flat face of original showed signs of impacting end of cylinder. A thin coat of tar on stock guide eliminated remaining twang.
Finally I also replaced the breach seal (flattened somewhat from sitting compressed for 6+ years after manufacture). Earlier tissue test of breach seal had been inconclusive. New seal made no difference in chrony numbers, gained peace of mind is all.
Overall pleasant shooter. Sharp report but now relatively mild mannered otherwise. 850 rounds through it to date, putting out approx. 14fpe with QYS 8.48gr domes.