This is because when installing the glass, there is stress somewhere, for example, the loose-leaf screw is screwed too tightly or not tightly, resulting in unbalanced internal stress and bursting. Or the internal stress in glass manufacturing cannot be completely released and balanced, such as short-time cooling. , causing the temperature difference between inside and outside to become the trigger point in the process of use, leading to bursting.

Or both.

The shape of the air gun shooting fracture is not like this. The contact (impact) point between the bullet and the glass should have an obvious center point, and the crack splits radially outward from the center point.