A bad trigger will prevent the gun from shooting as accurate as possible, but I haven't seen one that would make that much difference. Is it shooting off consistently in one direction or is it all over the board?

I would begin shooting at 25, then shoot at 50, 75, etc. working my way out. I have seen guns that, for some reason or another, cause the bullet to tumble end over end. I have a .22 pistol that does this. I set a target at 25, missed, moved to 10, missed, moved to 5 and hit all around the target. The bullets were tumbling. Every other bullet or so would enter sideways.