i wouldnt try to kill deer beyond 600 meters with a 6.5x55 even with carefully selected bullets and custom loads, the energy available to enable the bullet to do its job would most likely not be there to ensure consistant effective kills. you are talking about how much recoil will be there, most rifles able to kill at 1000 meters will boot. 1000 meter rifle .338 lapua mag or the .338 edge should see you right
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