He'd do slightly better than most criminals, then get killed by police. If it's in the US, the police have entered the 21st century and have stopped issuing S&W Model 10s. They'll have Glock of some sort, and a shotgun or assault rifle in the trunk. I'm not sure how well he''l be able to get headshots, considering said heads are moving and shooting back. Sure, he can shoot well while on a clock. Can he do the same while being shot at?
As for the highly trained team of military guys, try
The Kill Point. 6 ex-Marines rob a bank and it degenerates into a siege. They use a shotgun, a couple semi-only SMG clones, and one Type 56. Just ignore the worse-than-stormtrooper accuracy, the stupid police, the blatant continuity breaks, and the robber's leader more-or-less preaching to the gawkers. On second thought, the miniseries was terrible, don't bother watching it. A dozen cops, lying prone, can't hit the standing bad guys while firing on semi.
http://www.imfdb.org/wiki/The_Kill_Point
Any shoot-em-up robbery will end in a blizzard of police gunfire. you can't win.