Steve Donlon
Gold $$ Contributor
Years ago one of the guys that competes gave a review of seating depth for the new, at the time, Sierra 30 cal. 195 gr TMK bullet. He found .005 off was the spot. I tried it and it was the only place that worked for me also. My question is, as the barrel gets dirty that distance shortens from fouling. but it did not matter to me at the time. If you jam a bullet in a clean barrel, at some point after a few dozen rounds, won't that be really jammed and you need to force the bolt closed to chamber a round? I did a jam length test between a clean barrel and a dirty barrel and they were not the same length in my rifle.Personally, I’ve never found a single rifle I shoot for competition targets to shoot better with jumped bullets as opposed to shooting them .009-.018” off hard jam (using 1.5-3.5” of “neck tension”). I have tested lots of bullets out to as far as .120” off the lands and never found one that will consistently shoot. You may find a few small groups at a particular distance off the lands, but I think you’ll find as many large groups at that same distance. People can disagree all they want, and I’m sure some will, but having firing literally 1000’s of data points I could never convince myself this fallacy holds true.
Dave
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