Don't know how long I would carry this one concealed, but my HK USP Elite in 45 ACP +P having a 6+ inch barrel with O-ring lockup, adjustable sights and very nice trigger. I would have to go prone or to one knee at least and have the sights pre-adjusted for 50 yards.
Here's a story of an airman on base security (riding his bike!) near a base hospital taking down an active MAK-90 gunman from a distance 70 yards with his M9 service pistol on one-knee. He said he thought he could do it because he practiced privately outside of his normal duty requirements.
A significant event at Fairchild occurred on June 20, 1994 when Dean Mellberg, an ex-Air Force member entered the base hospital and shot and killed five people and wounded many others. Mellberg had been discharged after failing psychological evaluations by base psychologists Maj. Thomas Brigham and Captain Alan London. At the time of the shooting, Fairchild's hospital was an ungated facility. The gunman, armed with a Chinese-made MAK-90, an AK-47 clone[4] entered the office of Brigham and London and killed both men. Mellberg continued to move through the hospital, injuring and killing several people, including 8-year-old Christin McCarron. The gunman then walked out of the building into the parking lot, where after killing Anita Lindner, was confronted by Security Policeman, Senior Airman Andy Brown. From approximately 70 yards away, Brown ordered Mellberg to drop his weapon. After Mellberg refused, from a kneeling position Brown fired four shots from his 9mm pistol, two rounds hitting the perpetrator in the head and shoulder, killing him.[5] After an investigation it was concluded that Airman Brown was justified in his actions, saving countless lives, and was awarded the Airman's Medal by President Clinton.