To answer some questions, the box says, "Use only Alcan 209 Max-fire primers". How they will interchange with current 209's is unknown. Dude, will be returning in late October and will bring them for inspection. Additional reading says the hulls are aluminum with possibly a tin surface. Some have been shot and have developed small cracks at the mouth of the sell. A few appear to have been crimped and have developed additional cracks. Very tight fit in the chambers of my Sterlingworth from expansion. I don't think these are a practical substitute for brass Magtechs. Dude, save me a spot at Cowtown for November. Sagerider