I have several air Rifles. Crosman 2200, 180, Winchester 1000, QB78-T, B-20 and now a 1077. I have made every modification on the web to my 1077. I do have a stock valve spring. I have enlarged the ports in the valve and the piercing pin plug. The transfer tube is larger. After all, that I am still not happy with the way the shots group. One of the guys I shoot with seats his pellets in his springers. He feels that he gets better consistency. For me--- it didn't seem to make much difference -- UNTIL I tried it with my 1077. I have always made sure that the pellets are flush with the back of the cylinder. Today I made them flush with the front of the cylinder (side closest to the barrel). The groups definitely seem tighter. About 1/2 what they were. There is the occasional flyer. I think it has helped. Try it and let me know what you think!

There might be something to this. I fired off a bunch of clips (Gamo Match) - some with all aft, some with all forward, and some randomly mixed (you know, the "control group"). Using a Crossman Red Dot sight, there wasn't much difference at close range (~15 feet), however, the groups with the pellets pushed forward were noticeably tighter at 40 feet.
I'd be interested to see if this works with the CO2 pistols that use a similar-looking rotary clip.