The smallest 10 shot groups I can get is 1.25 inches at only 40 yards. A decent amount of my groups are more like 1.5 inches. I'm shooting 18.13gr JSB Jumbo Heavy in the low 1100s FPS and it's on the lowest power setting. I've been filling it up to 2600 psi then taking 10 shots then topping it off again. What can I do to make this thing shoot better?
Also, one really weird thing happened to me today. I left it cocked and closed in the rest and had to go do something and came back to finish my group and when I shot, it only sounded like a little “tink” and the bullet was so slow I could see it’s whole flight path and it hit very low. I tested this again and it only seems to happen when I leave the gun cocked for a while then shoot it. It's as if it it's getting very little air or something. But it shoots normally when I take the shot quickly after loading the pellet.