Camp, check out my post above...in factory loads, what you've "learned" is basically correct, the optimum bbl length for typical factory 9mm rounds is about 10-12" for maximum powder efficiency. However, if you load a slower burning powder to the maximum pressures that your RIFLE is rated to (typically considerably more than handguns), the 9mm +P+ becomes a much more viable round.

9mm for deer I see no reason. If it is all you have sell it and buy a nice 44mag lever It is quick cycling and very pointable in small barrel lenghts.

JMO. . . . .but I wouldn't do it . . . .the 9 just doesn't have enough juice. Law enforcment used to use alot of them, these days you hardly see any they all have moved up to at least a .40. If it is leagal and you must, not sure why, better be real close and make sure to hit him in the boiler room.