My office may have had a window shot. I don’t have a picture, but let me describe it and see if you think this sounds like a bullet vs some other object.
The window is about 8’ tall and 18" wide, located on the second floor. The impact site is waist high. The glass is about 1/4 inch thick. The outside of the window has a 1mm hole and the inside of the glass has a 1 inch diameter section blown out. It is a perfect symetrical cone with some glass fragments inside the building.
My thought is that something hit the outside of the window (a point of office debate). Given that the “cone” is perfectly symetrical the thought is that it is a bullet fired straight at the window as opposed to something such as a rock kicked up by a lawn mower or weed wacker.
Anyone have any thoughts? I have no experience shooting glass, save for bottles.
Are there any fractures from the cone? Specifically - are they radiating or concentric (or both)?
Any transfer (gray or copper) at the actual hole?
Though not always the case, a symmetrical hole/exit cone usually indicate a symmetrical projectile.
Whatever hit the window was low energy, or it would have penetrated. It’s amazing how a tire can “squirt” out a rock at a decent velocity, btw. How far away is the nearest street?
Probably nothing to worry about, at least not until you see lasers dancing around on your chest:)
The “exit” cone is a perfect cone. There is no splintering or anything. It looks almost surgical in its perfection. The 1mm hole is completely though the window. I didn’t see any evidence of lingering material at the edges of the hole. Nobody found a projectile.
The window is above a small parking lot and perpendicular to the road so it could not have come from the road itself. It overlooks a city yard where maintenance vehicles/tractors are parked. There is a 6 foot fence between the yard and the parking lot. This was discovered right after a Mardi Gras parade which took place about 100 yards from the building.
We have a window with a cone exactly like you describe inside our plant. Our door is completely inside, it was probably hit with something other than a bullet.
Been there, done that with a failure to follow the “know your target and what’s beyond” rule as a kid.
As a sidelight, I failed miserably at a story like Ralphie conjured up in “A Christmas Story” to cover my tracks. At least I didn’t shoot my eye out though…
Going by your description, since no photo is available, the first thing I would say is the hole is not a thermal crack.
The cone you described is caused by a high velocity impact. (The cone/crater is called a Hertzian cone).
Low velocity impacts create cracks in the glass that radiate out from the point of impact. IMO, this would rule out rocks thrown from tires or mowers.
The size of the hole and crater may be a different size than the diameter of the projectile, such as when the flank of the projectile hits versus the smaller diameter of the cross section, creating an oblong hole. A projectile will not create a smaller hole than its diameter.
I don’t think a BB caused it since the hole is 1mm and a .177 caliber BB is 4.5 mm in diameter.
I have a hole like that in my double paned Anderson window.
Small hole with spall on opposite side. The second pane wasn’t touched and glass fragments were trapped in the space between panes. There was no sign of the projectile that caused the tiny hole. It bounced back before making a full penetration.