I would not feel comfortable at all launching a 30-30 round in a school or mall active shooter scenario. The 5.56 mm is much cheaper to train with and does not have the penetration excesses of the 30 caliber rounds. In our enlightened hire them even if they are borderline qualified time, the 5.56 mm recoil is better tolerated than shotgun or larger 30 caliber guns.
We run our folks through a 800 round yearly refresher and quarterly training and quals. That would cost a lot more if we ran 30-30 or 7.62s. I doubt even the big boys would make it through 800 rounds of 30-30 in four days.
In all the law enforcement oriented training with the exception of firing from a helicopter, full auto is usually confined to CQB scenarios where two, two or three shot bursts are fired at across the room distance. Anything farther out is engaged with semi.
You have been watching too many hollywood movies if you think a trained officer will dump multiple magazines willy nilly across the neighborhood. Admittedly there have been incidents with multiple officers firing too many rounds with high capacity handguns but that is an issue of poor training and the exception rather than the norm. Even basic academy firearms training stresses accountability for each round fired.