Re: true bc of barnes 180 tsx?
Sorry, I realized I never answered your question. [img]images/icons/frown.gif[/img]
I haven't done any instrumented-type tests, but out to 800 yds Nosler's claim of .588 has been right on for me as accurately as I can tell from drop (correcting for conditions, of course).
.470 sounds reasonable to me for the 180 TSX--a lot more reasonable than what they advertise, that's for sure.
However, your experiment needs a control. Otherwise it could be blamed on other things like the clicks of the scope being off, etc, as others have mentioned. Doing the same test with one of the plastic tipped bullets would put those issues to rest.