From what I've read, with the proprietary powders and loading techniques Hornady is using, the 308 Marlin Express (with FTX bullet) is a lot closer to a 308 Winchester than a 30/30. Reports give it 2650fps with the 160gr FTX, which puts it just slightly above the 307Win and 300 Savage, and just below the 308.FWIW, That "Marlin in .308" ISN"T the .308 Winchester - it's a rimmed, lower-powered version (a kinda .30-30 on steroids) , the .308 Marlin.
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