Hope you have a few hours.

Kidding of course, but here goes. The 85CH has an abbreviatted hammer that still cocks all the way back, but is DAO only and cannot be cocked by hand. Don't even try or one will lose some flesh as well as have a nice nasty pinch wound to go along with the removed flesh.
The hammer is more recessed than on other DA/SA snubbies and is snag free on the draw or during firing. Can be shot through the pocket of a jacket if need be in an extreme case.So can the other models you have queried about. Have tried to get my unloaded 85CH to catch material while dry firing from inside a jacket pocket and can't get it to eat cloth.
The 850 has the recessed hammer inside the frame completely.Double action only as well as the 85CH.
851s have a shroud that covers the back, but have a bit of serrated hammer spur that sticks up out of the frame. This is for those who want to be able to cock the revolver for single action shooting and a more precise shot if time and events warrant it.
Don't let anyone kid you. Snubbies can and have been used for shooting out to as far as 100 yards and the target was hit repeatedly. Some emergency situations might actually need this feature. Hostage in front of a criminal and precise placement is needed. Or if that is the only gun on the scene and the criminal is some distance away. It has happened enough that gun tactics writers including Mas Ayoob, Clint Smith, and Chuck Taylor, all preeminent shooters and instructors in their own right, have documented such data on this.
None of these revolvers will catch on cloth or other things during a draw of the revolver.
Double action only revolvers stop an unwarrented attacks by defense lawyers and prosecution attorneys. These cases are made up saying that the person pre-cocked the hammer creating a "hair trigger" situation and the gun went off by accident killing or injuring the person shot. Trail lawyers do this to get insurance money by suing a person's homeowners insurance company, but you are the one being sued as well.
Overzealous prosecutors do it for many reasons. Don't doubt it.Remember the Duke la crosse team that was prosecuted for rape? Not only were the charges proven false and everybody knew it, but the prosecutor also knew that there was much evidence showing that no crime was commited at all.He kept the prosecution of the innocent players going for months. Ruined the team,coach,families, and players lives. So, it can and does happen frequently to be needed to be taken into account.
And yes as far as the revolvers are concerned, +P ammo can be used in any of them. Since the ammo (+P) is expensive, it is recommended that standard pressure loads be used for a majority of practice and 10 to 30 rounds of +P shot per session to keep current. There are standard pressure loads in the 110gr. JHP and slightly heavier that can offer a decent protection level if need be.
And there you have it from this source. Know for the others to chime in.
