If you hear hoof beats, suspect horses.
It could well be that the police called the projectile a .223 because that's what they were familiar with and they were dealing only with fragments, not an intact bullet. And besides, everybody knew it was a demented white military veteran. Where would he get an Ak-74?
Given that all the bullet "fragments" were recovered -
- what are the chances that they could state with confidence upon weighing the bullet fragments what the caliber was?
Also note that they have now had x number (what it it now - 11 different shots?) of opportunities to gather and weigh the bullet fragments from each of these shots - and it would be the 'graphing' (the plotting) of this fragment weight data that would be centroid on some weight (mass) value that would be indicative of the caliber of the rounds fired ...
except this IS for real .223 and it is a Romanian SAR 3(semi automatic rifle)....where the "3" tells you the caliber is .223. 1 = 7.62 x 39, 2 = 5.45 x 39.
One writer for Shotgun News has noted specifically(as have Second Amendment Sisters) that there ARE long barrel handguns available in this caliber that can be scoped & as accurate as many of the "M16-looking-things" they paraded on teevee. PLUS they are much more conceal-able.