After Columbine Law Enforcement started some serious testing on different calibers in building settings and more specifically Schools. They found pistol rounds, more so with 40S&W, had more over penetration in common building barriers then rifle and shotgun. Also pistol rounds caused more damage with skimming off hard surfaces, (the rounds bouncing down hallways stayed intact and penetrated more when they finally hit something square.) Hence the testing led to .223/5.56mm being standard issue to LEO. The fear of over penetration was dismissed and the value of a long arm dominated the debate with some Department heads, (DEA and FBI had pistol caliber carbines for a long time before they switched, the pistol caliber carbines are more likely to over penetrate when they aren't suppose to and under penetrate body armor when they are suppose to.)
Sheepdog keep up the good work.