Bayview Shooting: Explaining the Discrepancy Between SFPD Guns and Bullet Found in Kenneth Harding

UPDATE, 1:13 PM: Another possibility in this matter is that sometimes officers carry backup weapons on the job, with the approval of their departments. This would be, perhaps, a firearm purchased personally that can be carried on one's person while on-duty. I asked SFPD about this, and Sgt. Michael Andraychak just informed me that this was NOT the case with these two officers. Andraychak says the officers do not have backup weapons registered to them. Also, no other updates on the investigation that he knew of.

It's a key piece of evidence in the controversy over San Francisco Police fatally shooting 19-year-old Kenneth Harding: a .380 caliber bullet. The medical examiner's office says that bullet is the same caliber as a cartridge found in Harding's jacket pocket, but different from SFPD weapons.

Still, in the last few days I've gotten a lot of messages (particularly in response to my YouTube video with SFPD Chief Greg Suhr) asking whether a .40 caliber gun could fire a .380 bullet. In other words, could the bullet that lodged in Harding's head been fired by an SFPD gun?

"It's very obvious, the difference (between the calibers)," says Scott Jackson, chief handgun instructor at Burlingame-based Bay Area Firearms. Jackson says a .380 bullet would not work in the service weapons used by San Francisco Police.

"Their guns are Sig Sauer .40 calibers," Jackson says. "Standard-issue, period... If it's a completely different caliber than the duty-issued caliber of the SFPD, then it's very plain and simple that it wasn't fired from their gun."

A bullet's caliber is its diameter. That means a .40 caliber bullet measures .40 inches across. Jackson says a .380 caliber bullet is known as a "short 9", as in 9 mm bullet -- same diameter, but the .380 caliber has a shorter cartridge (holding the explosive powder behind the bullet).

Jackson says it'd be easy to tell the difference between various types of bullets, if you're trained. "We go over all the discernible differences (in our course)," he says. "We have trays full of spent cartridges, and... we show them the lengths of things."

SFPD initially thought a handgun recovered from a parolee's house was Harding's weapon, but the gun is a .45 caliber -- also, the wrong size. Investigators are still looking for the actual .380 gun that matches the bullet recovered from Harding's head.

More on the Harding shooting here.