Things I liked:Installed this into an RWS 34 Panther which is a well damped air rifle from the factory to start with. Shooting RSW Super domes it went from 926 to 940 FPS and shoots Predator PolyMags at 853 FPS (they shoot flatter for me). Analyzed audio recordings of gun before and after spring installiation. It does not make retort of the gun any quieter but it does dampen the spring noise. After the initial bang, there is less audio energy and it decays slightly quicker. You can feel the difference, what little spring bounce I had is gone. Also the spring noise from cocking is gone. If you need to replace the spring in your rifle, definately consider this. If you have a rifle that has a lot of spring vibration, get this spring now.
Things I would have changed:Tune it for the heavier pellets.
What others should know:The Panther has a synthetic stock that does not vibrate like some of the wooden ones do. The improvement should be much greater for those guns.
Things I liked:Quite operation and now cocks nice and smooth...elimated a crunching sound on cocking
Things I would have changed:Make it standard issue
What others should know:Spoke with the tech at Pyramyd, as I had to send this in to get installed, very helpful and even gave me some chrony numbers on how it was shooting..I didnt gain any spped, if fact lost approx 25'..but its made the rifle so much smoother...using it on a 34 panther. Fast turn around from Pyramyd.
Things I liked:Drop in replacement assm (with the right tools). VERY smooth with no "twang" effect AT ALL. Just a solid "thump". Cocking effort "feels" a wee bit stiffer although after 20 shots I got used to it as if it were the original. Makes a big difference in the feel of the gun firing.
Things I would have changed:nothing.
What others should know:Before the Pro-guide the rifle had about 1500 shots through it and could shoot 14.3 CP's at around 840- 850 FPS. I installed the Pro-guide and a washer as per BB's blog to try and get a little more velocity. Test fired about 5 shots for function and then set up the chrony. Did a 10 shot string and these were the results with 14.3 CP's: 1) 833.4 2) 838.4 3) 831.9 4) 837.8 5) 837.5 6) 842.0 (HIGH) 7) 825.9 8) 832.0 9) 837.7 10) 805.3 (LOW) Avg = 832.2 ES = 36.75 SD = 10.48 Not bad for a drop in spring/guide. Plus the "feel" of the rifle now is so good you want to shoot it MORE. I didn't get a chance to do any accuracy tests yet, hopefully it will shoot as good as it feels.