So, get an AR carbine in 7.62 NATO. Of course it will bite at both ends somewhat more than the .223, but heck *most* policemen don't shoot all that much anyway, and the recoil isn't going to bother those who do.
Did that, bought Armalite AR-10 carbine. It is real picky about what ammunition you use. Feels great, looks good. Would I trust it or my M1A if my life depended on it?? Never , I mean never had any round get stuck, fail to feed, fail to eject or just plain go bang when I shoot my M1A's. The Armalite loves to shoot expensive ammo only. I have lots of milsurp .308 and the M1A shoots everything I have ever put in it.