While it's true that the Model 59 was made before "+P" ammo, probably millions of +P rounds have been fired from the 39/59 series guns. Illinois State Police even used +P+ ammo in their alloy frame Model 39. I had a nickel Model 59 and a blue 459, both alloy frames, and didn't worry about shooting +P. I wouldn't make a habit of it, just for the price of the ammo, but I believe the gun would handle it all of the time.