So which guns are "safe" and which are not for the High Speed...
So as stated before, earlier S&W's used a different grade of steel and had different heat treating from that of the later "magnum" cylinders. Still, even an early J frame is not likely to have a catastrophic failure as the High Speed loads are very similar to a proof load. The issue is the level of safety beyond that which makes it a bad idea, and of course...the rest of the revolver. S&W made a calculated move with the 38/44 expecting that catastrophic failures were unlikely even in very early revolvers, and they were right (mostly). 5 shot J frames actually have a stronger cylinder than the K frames due to the offset cylinder bolt. Still, while the cylinder may not give way, the rest of the revolver just can't take it, and eventually you'll crack the frame under the crane...That goes for both J & K frame pre-war guns.
Colt's cylinders were full heat treated and there were no issues. Colt immediately "certified" all their .38 Special revolvers for the High Speed, including the Police Positive Special. And again, while the cylinder could handle the pressures just fine, the frame would break in exactly the same place as the S&W's. The medium frame Official Police and Officer's Model could handle all the High Speed you could throw at it.
So I'd steer away from the High Speed loads with the following...
Pre-War S&W J and K frames.
J frames made before the mid '80's (I can't recall the actual date that S&W certified all their J frames for +P)
Colt Police Positive and all the "D" frame revolvers on up to the mid '80's.
Charter Arms made before the '2000's
