The .05 is measured from the lands of the rifling, which should not be anywhere near the 2.734 listed in the manual. Basically what they mean is, if the bullet is seated long, it will jam into the rifling, and the round won't chamber. If you gradually seated the bullet deeper, till the bolt just closes, you are at zero jump. They want the bullet seated .05 deeper than that, so the bullet hits the rifling with a little speed, and engraves into the rifling instead of stopping, which would cause a pressure spike to get it moving again.
Because the tsx is solid copper, and not soft lead, it needs the jump. It is not just people saying that, it comes from Barnes. You might get away with less, but it is your face or eyes that catches heck if you don't.
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