Some years ago (mid eighties, if memory serves) my small 100 man department still hadn't made the transition to autos and we were required to carry revolvers. After a particularly ineffective shooting incident where two officers hit the target multiple times.... and the target then said " I guess you got me" and sat down to wait for the parameds... Some of our better trained combat types moved to carry either 44 (not allowed mag) or 45 long colt revolvers. Those of us that handled them at the range were impressed with everything about them for duty use.
That said, the real problem with a large weapon for off duty or concealed carry (whether officer or citizen)... is that you'll quickly find reasons not to carry that very good combat piece. It's just too big, too heavy, and unless you're a large framed individual that fine weapon won't be with you when it's likely to be needed most.
I carried a medium frame high cap 9mm or 40 cal for at least my last ten years in law enforcement. I carried, off duty, the exact same weapon I carried on duty - only in an ankle holster. Yes, it is possible to force yourself to become accustomed to something that most would find uncomfortable (nothing like living and working in a high threat environment to motivate you).
That said, most simply won't do it (and I still have the marks on my ankle almost 17 years later from carrying that weight on my ankle - and the noticable veins where the holster lay, even though I haven't carried a sidearm one time since I retired in 1995...).
Note: the 'target' I mentioned was the suicidal brother of a cop who dressed up in camo fatigues, called in a "man with a gun" incident, then fired several shots toward the officers as they approached on foot. Hit five or six times with 38 ammo in the torso - he survived the shooting in pretty good shape. Just one more thing to give a uniform cop bad dreams....
