For some reason all of my groups started getting really spread out - I'm talking going from 3/8" groups at 35 yards to groups that varied from 1" to 2" across. I could not for the life of me figure it out or how to correct it. I was about to do some troubleshooting including removing the barrel assembly. I noticed that the CF bottle would move up and down slightly. When I removed it the last time I screwed it in until it would no longer leak, but I didn't screw it in ALL THE WAY until it was tight and fully seated. I tightened it and low and behold, the groups tightened up - went back to normal. Bear in mind, the bottle was not leaking, just not screwed in tightly. The only thing I can imagine is that the slightly loose bottle set up a weird harmonic when I fired. Once fully tightened, the slight wiggle was gone and the (assumed) harmonic was no longer there.
