Lesson Learned: If you drop your calipers, check the zero

As I pull pistol cartridges off the LCT press, I drop them into plastic ammo boxes that are a 10x10 grid. I check one cartridge out of each row for OAL and powder charge. Typically if my OAL changes as I load, it gets longer due to the seating stem backing out a little.

Tonight I saw a pretty dramatic change in the OAL, stopped and adjusted my seating die down and loaded a few more cartridges. When I checked the next cartridge, it measured at the correct OAL, but just LOOKED way too short.

Then I realized at some point, I'd dropped the calipers off my workbench and decided to check the zero. Not only were they not zeroed, but they also COULDN'T be zeroed. Every time I would adjust it, and then check it again, it would give a different reading, so something inside broke.

Tonight I'm loading 10mm: a 200-grain XTP over a max charge of Longshot. I'm not sure if the offending cartridges are short enough to be a problem, but don't' aim to find out. My new calipers should be here Friday, and I'll get the bullet puller out for any that are too short.

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Originally Posted by Lester Polfus

Tonight I'm loading 10mm: a 200-grain XTP over a max charge of Longshot. I'm not sure if the offending cartridges are short enough to be a problem, but don't' aim to find out. My new calipers should be here Friday, and I'll get the bullet puller out for any that are too short.

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If you are using an inertia bullet puller at least that should be pretty easy with 200g bullets. You might even be able to tap a few out and reseat them properly?

Maybe I make it harder than it has to be, but I use vernier micrometers as opposed to calipers. Nice thing about vernier micrometers (and calipers) is that unless you bend them, it is really hard to knock them out of calibration. They also make inspection very easy as excessive thimble movement in either direction is a snap to detect.

I have learned the hard way to not trust dial and/or digital calipers. Everything from debris in the track to broken gear teeth has caused me issues with some rather costly workpieces. I bought 0-1" and 1-2" vernier micrometers from pawn shops for less than a set of calipers would cost and checked them against a set of gage blocks at the office. The 1-2" is an old Brown & Sharpe that was still in its factory case and the carbide faces were in good shape.

Something like these would be good for many pistol cartridges. https://www.amazon.com/dp/B01548KFMK/ref=biss_dp_t_asn

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I'd dropped the calipers off my workbench and decided to check the zero. Not only were they not zeroed, but they also COULDN'T be zeroed.

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A machinist said, "If you drop your micrometer, dust it off and check the zero. If you drop your dial calipers, walk around them on your way to get the spare."

This is good info regarding micrometers vs. calipers. Thank you all. I think I'll get some.