The frame relation to the slide is controlled by the slide guides on the frame. While these leave the factory good enough to function most Glocks wont shoot better than 3" and more like 4 1/2" at 25 yards. Fine for fighting or defensive use but if you are trying to cut the aorta off a deer heart at 40 yards not the perfect scenario. The first step to making one shoot bugholes is making sure that the guides are all on the same plane. If you are not very familiar with this step don't attempt it. It is easy enough to check with a piece of glass by removing the slide and placing the frame rails against the glass. if it wobbles more than .008" it isn't going to be a bug hole shooter. The way you check it is with a feller gauge under one of the guides if it rocks.

Midwayusa has the Timney triggers in stock most of the time.