I have a s&w model 36 that was made in 1964. I would like to keep some +P ammo for it, mostly for home defense. Even though the current model 36's are rated for +P, S&W says that this gun is not. Of course there was no such thing as +P in '64, but some have said that the current +P loads are equivalent to the older .38 standard loads. Is this true? I don't want to risk damaging the gun. Any thoughts?