The S&W M19 and 66 are fine guns and while certain parts such as barrels are no longer available, those parts are commonly worn out or broken with normal use. So long as you don't abuse the gun and keep Magnums with bullets lighter than 140 gr out of it, you're highly unlikely to ever have a problem that a competent gunsmith or the S&W factory couldn't fix as common wear parts like hands and cylinder stops are interchangeable with other K-Frames.
The Colt Trooper and Lawman, as have been mentioned, are also excellent revolvers but I'd be a bit more hesitant to recommend one for a "working gun" over a S&W for a couple of reasons. First, there is more than one version of both revolvers and while they share names, they are actually very different internally. The original Trooper and Lawman used Colt's older double-pawl lockwork much like the Python and Official Police. While these guns are not as delicate as some claim, they are slightly more prone to timing problems than a S&W or Ruger. Also, they lock up differently and conditions like slight rotational play in the cylinder at full lockup, which would be perfectly normal and acceptable on a S&W or Ruger, are indicative of major timing issues which require the attention of a gunsmith.
Starting with the Trooper/Lawman Mk. III and continuing through the Trooper Mk. V and King Cobra, Colt changed their lockwork to a simpler design more akin to a S&W or Ruger. While Colt enthusiasts don't find these guns quite as desirable as the earlier versions, they are in fact very good guns that are probably stronger and more durable than their predecessors. I personally have always liked the look of the Mk. III in particular due to their half-lug barrels (probably because I'm a S&W guy). One important caveat, however, is that these revolvers should not be dry fired without snap caps as they are prone to break firing pins if such is done and Colt are the only ones with the tools to replace them.
With any Colt DA revolver, my main concern would be the availability of parts and the fact that few gunsmiths are qualified to work on them. While they are fine guns that I certainly wouldn't mind owning and shooting occasionally, for a gun that will be shot and/or carried regularly I'd personally prefer one that can be readily serviced if need be.
The Colt Trooper and Lawman, as have been mentioned, are also excellent revolvers but I'd be a bit more hesitant to recommend one for a "working gun" over a S&W for a couple of reasons. First, there is more than one version of both revolvers and while they share names, they are actually very different internally. The original Trooper and Lawman used Colt's older double-pawl lockwork much like the Python and Official Police. While these guns are not as delicate as some claim, they are slightly more prone to timing problems than a S&W or Ruger. Also, they lock up differently and conditions like slight rotational play in the cylinder at full lockup, which would be perfectly normal and acceptable on a S&W or Ruger, are indicative of major timing issues which require the attention of a gunsmith.
Starting with the Trooper/Lawman Mk. III and continuing through the Trooper Mk. V and King Cobra, Colt changed their lockwork to a simpler design more akin to a S&W or Ruger. While Colt enthusiasts don't find these guns quite as desirable as the earlier versions, they are in fact very good guns that are probably stronger and more durable than their predecessors. I personally have always liked the look of the Mk. III in particular due to their half-lug barrels (probably because I'm a S&W guy). One important caveat, however, is that these revolvers should not be dry fired without snap caps as they are prone to break firing pins if such is done and Colt are the only ones with the tools to replace them.
With any Colt DA revolver, my main concern would be the availability of parts and the fact that few gunsmiths are qualified to work on them. While they are fine guns that I certainly wouldn't mind owning and shooting occasionally, for a gun that will be shot and/or carried regularly I'd personally prefer one that can be readily serviced if need be.
