Molly: Groove

The Molly Groove has a secret personality, though. It only appears if you shoot lead bullets. If you shoot copper-jacketed bullets, the harder metal bridges the groove, and the bullet comes out looking nearly pristine. This means the gun is a chameleon: sometimes it leaves a perfect clue, sometimes it leaves almost nothing at all.

If you find a bullet with exactly heavy groove and the rest smooth or faintly hexagonal, you can instantly identify the family of firearms (certain Glocks, for example) and even the specific brand of aftermarket barrel. In one famous 2019 case in Arizona, a shooting suspect claimed his gun was a "common model." But the Molly Groove on the recovered bullet was positioned at 22 degrees offset from the extractor mark—a unique anomaly from a worn tool in the factory. That groove convicted him. molly groove

To understand the Molly Groove, you first have to understand a dirty little secret of firearm engineering: lead bullets are messy. As a bullet travels down a rifled barrel, the soft lead can strip or melt, leaving a residue of “leading” behind. To fix this, many modern handguns (like the Glock, Smith & Wesson Sigma, and Kahr series) use a specific type of polygonal rifling. The Molly Groove has a secret personality, though