FYI, if you consider 100% to be the maximum ability for accuracy increase in a KSC Glock, 10% is barrel cleanliness, about 20-30% is a tightbore installed, and the rest is ALL about inner barrel stability. With a safe, unloaded Glock, look at the muzzle of it and stick something like a pen into the inner barrel, and move it around. You'll see there is about 1mm of play in every direction. Install a larger O-ring to stabilize it, or wrap the inner barrel just behind where the O-ring sits and add enough tape to be able to get it back in the outer barrel so it doesn't move around too much. Best to add a bit more tape than you need, then peel back a half inch at a time and cut off. This will greatly increase accuracy more than any tightbore can.
Another tip, Glocks tend to shoot about 2" low at 30ft, so learn to shoot it this way: Line up the bottom of the front sight's dot with the top part of the rear sight. Using heavy BBs (over 0.28g) you can easily get man sized hits past 100ft. Aim for the head, hit the chest, even with a bone stock KSC Glock 19.
This post should be a sticky. Lol