I usually check every 10th one but use a flashlight to look at all of them when they're together in the loading block. If I were on the ragged edge I might weigh every one. A lot depends on how nicely the powder meters. H335 vs 4064 or unique, for example.
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I weigh about every tenth unless I'm pushing the upper limit, then I check every fifth. I also installed a short strip of LED white lights in the top of my press so I can visually check that powder is present before seating a bullet.
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I weigh them at random.
Terry
When I was chasing tiny groups in a rifle I would weigh every charge in addition to sorting brass by weight/uniforming primer pockets/ deburring flasholes/turning necks.
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And then there's those who shoot Greek military surplus .30-'06 from an 81-yr-old Garand and still manage minute-of-buffalo accuracy with iron sights at 1,123 yds.
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In my closet, yes. Other than that, anybody's guess. I think CMP ran out of it several years ago unless they found another stockpile.