Disco has never been accurate.

I have had a .22 Disco for about 2 1/2 years now. I noticed right after I put a scope on it that the gun just wasn't very accurate. It has never been much more than good enough to racoon hunt since. I feel I have done everything besides change the barrel to try to improve the accuracy. Ive modded the trigger to about 1 1/2 lbs. Smooth,light and predictable. Opened up the valve & enlarged hole a wee bit and put icemaker transfer port in to make volocity a consistent 950 fps., Put a heavier hitting hammer spring (no more quiet, weak shots here and there) , Lapped and recrowned the peeshooter, Tried 5 different scopes on it thinking I had a string of bad scopes(its happened to me before). Nothing seems to keep this Disco from shooting in roughly 3 inch circles at 27 yds.. I hate to admit this airgun has beaten me. I can't seem to make her shoot an accceptable group. I'm at a loss. Is there something I don't know about Discos ? Otherwise I remain unimpressed with them eccept they are fun to take apart and put back together. lol For God sake, I have magnum springers that will outshoot this thing. Thats pretty sorry for a PCP. Please help !