You can carry with a round under the hammer in any revolver except an old stype 3 screw Ruger or Colt SAA. No double action can hit the firing pin on the primer without pulling the trigger. The hammer is cammed away. Transfer bars are safest, of course, but don't worry about your Colt DA.
Actually this isn't quite true. The Smith & Wesson revolver originally used the rebound slide to block the hammer to provide a "safety" and this design resulted in, I believe, a British Naval Luetenant being killed when he dropped a Victory model on a steel ships deck. What happened is the hammer piviot pin sheared and this allowed the hammer to come forward and fire the gun. Post WWII S&W revolvers implemented a sliding positive hammer blocking safety that places a tab of steel between the base of the hammer and the frame. BTW, this new sliding hammer block was why post WWII S&W's carried a leasding S in the serial number post WWII and into the 50's to siginify that new safety feature. As for older Colt revolvers, I'm a S&W junkie and don't know much about Colts at all, to those into the S&W revolvers purchasing a Colt is considered "going over to the Dark Side".
However, I firmly believe that you can only be safe with any firearm once you've done your due dilligence and looked into the particulars and history of what you intend to carry. Until that Leutenant was killed S&W considered it's use of the rebound slide to block the hammer to be perfectly adequate, as did most police agencies. After that incident, all S&W DA/SA revolvers carry the hammer block to this day and it's a very clever and positive safety that has no effect of trigger feel and is only a minor inconvenience when mounting the sideplate. Personally, I wouldn't carry a S&W revolver that didn't feature this hammer block, while that incident was likely a "just wrong" drop of the gun why take chances when there is no need for it, there are plenty of used model 10's and others available with this safety at very reasonable prices.
As for that MSP officer stating it was illegal to carry with one in the chamber, NOT true and a bit surprizing. I know at one point the issue sidearms for the MSP were Sig Sauers with a rather heavy DA trigger. Perhaps they've gone to Glocks and he's seen all the Glock Leg incident posts and now carries with his chamber empty. If so, I sort of understand it because I prefer a Sig for carry over any other semi, simple revolver like manual of arms and no safety to remember to flip off. However, being up to speed with the manual of arms and paying attention can make carrying a Glock perfectly safe to carry with one in the chamber.
