SAAMI diameters for .38 Special and 9x19 are the Same (Lands, Grooves, Bullet) if those bullets are the same weight and composition thier lengths are quite similar indeed. Because most 9x19 rounds feed from a magazine to a chamber thier OUTSIDE curvature and crimping are design criteria insignificant for .38 Special. Most of the revolver HP ammo I have seen has larger metplats and cavities than same weight semi auto HP ammo.

And while Velocity is a "sexy" measure, it comes and GOES fast. Momentum is what drives the bullet to penetrate deeply. Momentum is aided by bullet weight.

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Certified Curmudgeon