When I first got into PCPs I didn't know much about them. I had narrowed my selection down to the Air Arms S500 and the Weihrauch HW100. The S500 is a beautiful and capable airgun but I decided that the HW100 was the best choice for me because it was regulated and has a superior magazine system. I've never regretted that decision.
Fast forward a number of years and I was still looking and reading about that Air Arms PCP so the itch was still there. An opportunity came up and I bought the (now regulated) S510 in walnut. Unfortunately the walnut stock doesn't fit me and I had to upgrade to the adjustable laminated one.
The S510 is a beautiful PCP, it's well made and accurate. But I have to say that I'm a bit disappointed with my decision as it was mostly made on esthetics, my bad!
Nothing wrong with the S510, it's a fine airgun, but it's an old design (based on the 400) that has been upgraded to keep up with the times. I don't care for the magazine system, it works but it's delicate and seems like an afterthought to turn single-shot into a repeater. My FAC version seems to be a sub-12 fpe design with a stronger hammer-spring and the regulator set high.
Guess the my tastes for modern, adjustable PCPs is showing. I'm not one to sell or trade my airguns but I've never really "bonded" with the S510 and it may be moving on. My regret is more with my decision than the airgun itself.
Cheers!