Maybe by certain Mfg, but the one stamped on my tikka is wrong. Not only did the cleaning rod test give a longer result, but the bullets that the calc said would be too long based on the cleaning rod measurement showed wildly erratic flight past 500 yds.
Take a cleaning rod with a free spinning handle. Attach whatever fitting you have that gives the tightest fit in the barrel. Shove it a little ways in the barrel. Make 2 marks on the rod indicating the depth of the rod and the 12:00 position. Run the rod in until it reaches 12:00 again, then mark the depth again. Remove and measure the distance between the marks, and you’ll have the inches per 1 full revolution. (12:00-12:00)
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