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Old September 24, 2011, 10:08 PM   #1
Brian Pfleuger
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Ever Measured Finished Round Weight Variance?

I was curious, so I checked my finished batch of 7mm-08 hunting rounds.

The load is Norma brass, CCI BR large rifle primers, 41.7gr IMR 3031 and 110gr Barnes TTSX bullets. It's a small batch, just for sighting in, but I found:
  1. 323.4
  2. 323.7
  3. 324.0
  4. 323.6
  5. 323.6
  6. 323.8
  7. 323.4
  8. 323.4
  9. 324.1
  10. 323.9
  11. 323.1
  12. 323.9
  13. 324.0
  14. 323.5

For an average of 323.676, a SD of .303 and a max spread of 1.0gr. That seems like very low deviation to me, with a minimum of just .6gr below average and high of .4gr above.

What say you?
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Old September 25, 2011, 12:31 AM   #2
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That's not too bad.

I get more variation sorting unprimed cases from the "lesser" manufacturers (R-P, Win, Federal, etc.).

The best I've ever had (empty, unprimed cases) was an extreme spread of 0.1 grains, with a 100-piece lot of Lapua .30-06.
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Old September 25, 2011, 02:15 AM   #3
Kyo
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i checkmy 45's sometimes. Its the quickest way to see if you double charged. Which I never have, but when I am not sure for whatever reason, the scale comes out. Its consistent. Its just like OAL, as long as its within a range I don't care
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Old September 25, 2011, 04:44 AM   #4
BDS-THR
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Unless you weighed the cases before charging with powder, finished weight variations could be from case weight variations. For some test load development, I will weigh trimmed once-fired cases to same weight range within 1 grain. Not sure how much weight variations in case weight affects target accuracy.

As to 45 cases, they will vary several grains depending on headstamp and lot. If powder charges were around 5-6 grains, it may be hard to detect whether the finished round weight variations were from case weight or powder charge.
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Old September 25, 2011, 06:26 AM   #5
dmazur
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Depending on bullets, I've found bullet weights can also vary a few grains. Taken together with case weight variation, you can have results that generally don't mean anything.

Well, unless you weigh each case and each bullet...but if you're that compulsive, I submit that you probably are meticulous in your reloading process and don't need to weigh completed rounds for reassurance.
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Old September 25, 2011, 08:13 AM   #6
Brian Pfleuger
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I did it purely of curiosity. The charges were all dispensed by an RCBS 1500, so I'm not worried about charge variance. What really gets me is that several of the cases have clean primer pockets but many do not. I almost believe that I could pick the clean ones just by weight.
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Old September 25, 2011, 09:31 AM   #7
Skadoosh
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As has already been mentioned, I too only ever weigh a finished round if I suspect a double charge. Finished round weight variance is pointless unless you weigh each component separately beforehand.
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Old September 25, 2011, 05:46 PM   #8
Brian Pfleuger
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Quote:
Originally Posted by Skadoosh View Post
As has already been mentioned, I too only ever weigh a finished round if I suspect a double charge. Finished round weight variance is pointless unless you weigh each component separately beforehand.
Curiosity is never pointless, my friend.
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