I own a dozen magnum revolvers. I reserve magnum loads for magnum duties....that doesn't include paper punching or steel banging.

When my M&P340 goes to the range I shoot 50 regular 38 loads thru it. The last cylinder full of 38's will go into 2" @ 30 feet. I wrap up with 5 light magnum handloads that duplicate my carry load ... those 5 also go into a 2" group. If I were to keep shooting, no doubt the magnum groups would open a bit.

I don't buy into the "practice with what you carry" camp. There's much more to learning to shoot quickly and accurately with a J frame than managing recoil. I know that a few hundred rounds of 38's a year insures those 5 magnums will surely go where I intend them to go.

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Carry.."hope" isn't a strategy