Hello Frank, no fire proof clothing needed. I have never heard of K38's having any special treatment to enhance their accuracy. I think that like most S&W revolvers the design and manufacturing process is just inherently good and with some exceptions the SW revolvers are among the most accurate handguns built. The K38's were and are considered "world class" by serious target shooters. I think as much as having accurate barrels the smoothness of the action and excellent triggers contributed to their reputation. As far as twist rate I will leave that to a more knowledgeable member.

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John. SWCA #1586