To me it sounds like the pellet probe depth might be way off. I've been tinkering with mine trying to get a little more velocity out of it. After visiting back and forth with Chuck through PM's he explained and I REALLY believe it now that if its off even a tenth of a millimeter that can make a HUGE impact on velocity, the cocking of the gun and releases of air back out the receiver. He explained that if you take the gun apart even just removing the air tube and reinstalling it that can affect the probe depth and it must be check and possibly re-adjusted and I suspect the deeper the gun is taken apart the better chance that the probe depth might be off. Here is Chucks description and procedure for checking this measurement. Hope you don't mind Chuck.
"One of the peculiar things about the design of the Wildcat is that the feeding pin (aka pellet probe) has a hole in the end of it the same size as the hole in the barrel inlet – these holes of course are referred to as the transfer ports. It is critical to have the hole in the feeding pin exactly centered over the hole in the barrel inlet. This feeding pin must be set to a certain tolerance and if it is misaligned even a little it will cause you big problems. This misalignment results in the feeding pin partially blocking the air coming up from the barrel TP hole…and even blocking the hole a thousandth makes a huge difference, and it can drive you crazy trying to figure out why your velocity is so terribly off. If the misalignment is too pronounced the hammer will not catch on the trigger sear when you try to cock the gun. One of the flaws in the design of the MK1 is that the gun will actually cock and shoot with this feeding pin hole misaligned slightly.For an example, imagine taking your gun apart to put a new o-ring on your regulator…and then putting your gun all back together. Before you took it apart it was shooting 25.4gr. Kings at 920 ft/s…but when you put it back together it shoots them at 675-700 ft/s! You know something changed but you don’t know what. When this happened to me the first time I went crazy trying to figure out what was causing this problem. In frustration and disgust I mailed my gun to AOA to have them fix it…and an arm and a leg later I got my gun back shooting correctly! Later I discovered out how to correct this problem and I will share this secret with you now. On your calipers there is a depth gauge on the one end that you can use to measure the setting of your feeding pin. Simply measure the depth by inserting the depth gauge in the hole at the rear of the breech block so that it is touching the rear of the feeding pin, and then slide the calipers up against the block. The measurement should be between 28.55mm and 28.8mm. To set this correctly you can set your calipers to say 28.55 and lock down the little stop screw. Next take a 3mm Allen key and loosen the two set screws on the “reload sliding bracket” (C9 on parts diagram). Now push the depth gauge against the rear of the reloading pin…there is spring pressure from the spring inside the “reloading bar guide” (C14 on parts diagram). So then, push against the feeding pin with the depth gauge until it butts up against the rear of the breech block…and while holding pressure on the depth gauge use your left hand to tighten one and then both of the set screws on the “reload sliding bracket”. Recheck your depth with your gauge and repeat the process until you get it right. The room for error is only .25mm…so do this carefully! For a depth gauge you could make a depth gauge on a lathe…or a bolt cut off exactly to the correct length with a large head on it that you could push in the hole against the feeding pin until the bolt head stops against the rear of the breech block. But it has to be repeatable so you set it to the same place each and every time. To see how critical this is, try deliberately setting the feeding pin to the wrong depth…say 28.0mm or 27.5mm and shoot your Wildcat over your chrono, and see the difference in velocity for yourself.Setting the depth of the feeding pin correctly also sets the Wildcats cocking mechanism correctly so that when you pull the lever back the hammer catches on the sear correctly at the right spot".
Chuck, through his trials and tribulations has been a huge help to me so maybe this will help you too. Thanks Chuck....
Jimmy
