so same material and process to make a model 19 cylinder was used for the model 10 cylinder (except for size) and the model 10 "can't" shoot" .38 +p?
not exactly.
First off, there is a difference between the model 19 and model 10 cylinders, and that is the heat treatment S&W applies. They aren't the same. Magnum cylinders get a different heat treatment than standard calibers.
Does this make a difference? I'd say at .38+p pressures, no, but at magnum pressures, yes.
second, S&W is not saying you cannot use +p in the model 10. They are saying they don't "rate" or "certify" the model 10 for +p ammo.
The difference is subtle, but important.
What is missing is the explanation WHY S&W doesn't rate that gun for +p.
It has nothing to do with the gun's strength, it has to do with legal liability.
S&W never tested the model 10 with +p ammo. And since they never did their own tests, they will not rate/certify the gun for ammo they didn't test in it, on the record.
Off the record, guys who work there will tell you the gun is plenty strong enough, and you can look at NY, Chicago, and LA PDs using those guns with +p ammo for decades without issues due to +p pressures.
I personally wouldn't hesitate to fire them from time to time in any S&W or Colt made since World War II. The gun is not going to blow up in your hand. In THEORY, if you shoot enough of them, you might loosen the gun up to the point you'd have to have some maintenance done. That would probably take about a truck-load of ammo, but you could probably do it.
I pretty much agree with this, but it may not take a whole truckload of ammo, depending on the specific gun. For example, I have a Colt Agent .38 (alloy frame Detective Special). Back when Colt was making them, they DID rate the gun for +p ammo.
HOWEVER, they asked that at 1,000 rounds you return the gun to Colt for inspection, and possible repair. And every thousand rounds there after, as well.
Very few people would ever hit that round count from that kind of gun, but if you did, Colt wanted to check the gun, just to be sure everything was ok.
Personally, I put 1,000 rounds far below a "truckload".