I wanted to see what was the max efficiency I could get for a classic valve on a 12 gram. My set up is a standard classic AIR valve ser# CF07798, L7 bolt, (8) 3/8" ID nylon washers, Crossman 12g, RT on/off .750 pin, CCI 12b quick changer, macro line, and a piece of weed wacker string to de-volumize the macro line. Shots where 5-8seconds apart. I didn't have a chrono, but instead relied on the old "put 4 fingers in front of the barrel about 2" from the front technique. By the force felt on my finger I could tell my pumpmag was firing at or above 285 fps. Scientific? not by a long shot, but most of you reading this and comprehending what I'm saying have also used this refined technique in the past. The total shot count where 30 usable and 3 flea farts. I hope to do a vid over the chrono with Zman in the near future to get exact fps and usable shots. Also note I was unable to get the same velocity with HP air, but by subtracting washers you can reach a medium between co2 and hp. The downside sill be less of a shot count from a 12g of course. I plan on playing strickly SC so I'll stick with the 8 washers. I could probably ad 1 maybe 2 additional washers and get a few more shots, but I decided not to since I'd rather have a wider velocity range in case of cold weather.