Hate to tell you but both you and Rossi are wrong. The S&W safety device is properly called a "transfer bar." According to SAMMI, a "transfer bar" shields a firing pin attached to a hammer and a "hammer block" shields a hammer from striking the firing pin mounted on the frame. They both do the same thing, but because the firing pin is located in different places on their respective revolvers, the shielding is performed differently and called by different names. Maybe you can "Save Face" by telling the NRA Riflemen of the error in calling the item a "hammer block" in the article which it is not.
SAAMI, not SAMMI.
I searched the SAAMI website and found a definition for hammer block safety.
A device intended to isolate the hammer from the firing-pin except when the trigger is pulled.
saami.org
A device intended to isolate the hammer from the firing-pin except when the trigger is pulled.
That definition is correct, but it is so vague that it is totally useless for differentiating the two types of safeties.
I was unable to find a definition for transfer bar safety on the SAAMI website.
The explanation you provide is incorrect. A transfer bar doesn't shield anything, in fact it isn't between the hammer and the firing pin until the trigger is pulled. A hammer block does perform a shielding action. A hammer block can be used on a firearm regardless of whether the firing pin is on the hammer or mounted to the frame. A transfer bar only works on firearms with frame-mounted firing pins. It is true that they both do generally the same thing (prevent the gun from being fired if the trigger is not pulled), but they do it in very different--one might say, opposite--ways.
Here are correct definitions/explanations.
A transfer bar TRANSFERS the hammer blow to a firing pin. That's why it's called a transfer bar. The hammer can't reach the firing pin in a transfer bar design unless the transfer bar is interposed between the two. When the trigger is pulled, the transfer bar is
moved between the hammer and firing pin and allows the hammer strike to be transferred to the firing pin. A transfer bar is, in the normal state, not obstructing/shielding anything--if the hammer were to fall unintentionally without the trigger pulled it would not hit the transfer bar--it would hit against the frame. Ruger revolvers are equipped with a transfer bar.
A hammer block BLOCKS the hammer so it can't reach the firing pin, or (if the firing pin is hammer-mounted), BLOCKS the hammer so the firing pin can't reach the primer. That's why it's called a hammer block. While the hammer block is in place, the gun can't be fired because the hammer block shields the hammer from hitting the firing pin or blocks the hammer so that the firing pin can't hit the primer. When the trigger is pulled, the hammer block is
moved out of the way allowing the hammer to strike the firing pin or the firing pin to strike the hammer. A hammer block is, in the normal state, obstructing/shielding the hammer and is moved out of the way to fire the gun. If the hammer were to fall unintentionally without the trigger pulled, the hammer would hit the hammer block which would stop it from hitting the firing pin or prevent the firing pin from hitting the primer. S&W revolvers use a hammer block safety.