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Posted: 5/20/2008 1:48:22 PM EDT
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I loaded my first 10 rounds of 9mm last night. One thing I noticed is that the overall length of the cartridge would vary if I measured it several times. I was looking for and OAL of 1.12. If I measured the same cartridge several times I would get 1.11, 1.12, 1.14 and so on. It seems the caliper is measuring the imperfect top of the FMJ bullet. Is this normal? Will these variations cause pressure problems? TIA |
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That variation is caused by the force you're using to close the calipers and/or the nonuniform and springy nose of the bullet, plus a little misaligment of the calipers thrown in for good measure. Close the calipers gently, then mash them closed; you'll see the measurement change at least 0.0005 inches with digital calipers. Part of the point of a load workup is to find a robust load that can absorb the minor and normal dimensional and charge weight variations safely. Don't worry about 0.002 inches, particularly when it's to the long side, unless it affects feeding of the cartridge through a magazine. |
| If it jumps around, up and down, when you measure that's normal ... like Aero said just hitting high and low points on the web or bullet tip. If it gets smaller every time you measure though you don't have enough neck tension and you're pushing the bullet back into the case a bit each time you clamp the calipers. |
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