Mr Infidel sir:

Read top article first. There is a chart a little way down the page with +P and +P+ velocities and pressures. ( I am an old fuddy duddy, my advice is If you want to feel right about new guns fire target loads for awhile) (Treat them like a woman - don’t stress them out and they will not stress you out)

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Overpressure ammunition - Wikipedia, the free encyclopedia