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Old 01-23-2013, 16:47   #1
TDC20
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Join Date: Apr 2011
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Has anyone measured jacketed bullet diameters?

The other day, I loaded up 50 Nosler 135 JHP's and then loaded 50 Sierra 135 JHP's. I noticed during crimping that the Nosler loads were rarely ever touching the Lee FCD sizing ring, while almost every Sierra round lightly brushed past it. Out of curiosity, I measured the diameters of the two unloaded bullets, and found that the Sierras were precisely .4000" with no measurable variation, while the Noslers measured between .3993" to .3998", with the average around .3995". I also had a box of Nosler 150's open nearby, so I checked a few of them, and they were about .0005 too small on average, also.

I checked some Hornady 180 and 200 XTP's, and they were exactly .4000" and very consistent like the Sierras. I also had a few 180 GDHP's, and they measured very consistently at .4005". I had a box of PD 180FMJ's, they measured .4003" to .4005", most of them closer to .4005"

So, has anyone else noticed this before? I couldn't find any history on the subject in a forum search. All this time, I thought that the 135 Noslers weren't very accurate because of loading them to hyper velocities. Now I'm wondering if the issue might be undersized bullet diameter.

If anyone out there has time to measure some unloaded bullets from various manufacturers for diameter, I'd really like to hear your results. The fact that the Nosler 150's measure small also makes me wonder if this is a fluke lot of bullets, or if it's widespread on all Nosler .40/10mm bullets.

It's a good idea to keep this in mind when changing bullets on a specific load. It could get you into some pressure trouble unless you back off a bit and work up again with the new bullet.
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