I'm no lawyer but I can easily see how using the same exact weapons your PD uses could be used against you....
"Look at this guy, he thinks he's a cop. THAT'S why he shot this poor, innocent choir boy, who just happened to have noticed the broken window and was crawling in to alert the homeowner."
I'm pretty sure most anything can be used against used by a prosecutor so-inclined. Your safest bet, in my estimation, would be to use something popular and common among "regular" people. A "normal", unmodified gun. "Normal", commercial ammo.
I am not saying that it couldn't happen, but IMHO I find that to be a much more unlikely outcome in the case of a handgun or shotgun. But, then again, most police departments use handguns and shotguns that are common in the civilian market. I think it would be positive support to your argument that you use what your local police use. If they did accuse you in the manner that was stated, it could easily be presented in a more positive light by the defense.