Ever Measured Finished Round Weight Variance?

Brian Pfleuger · September 24, 2011, 10:08 PM

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:

323.4
323.7
324.0
323.6
323.6
323.8
323.4
323.4
324.1
323.9
323.1
323.9
324.0
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?

FrankenMauser · September 25, 2011, 12:31 AM

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.

Kyo · September 25, 2011, 02:15 AM

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

BDS-THR · September 25, 2011, 04:44 AM

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.

dmazur · September 25, 2011, 06:26 AM

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.

Brian Pfleuger · September 25, 2011, 08:13 AM

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.

Skadoosh · September 25, 2011, 09:31 AM

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.

Brian Pfleuger · September 25, 2011, 05:46 PM

Quote:

Originally Posted by Skadoosh

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.

September 24, 2011, 10:08 PM	#1
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	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: 323.4 323.7 324.0 323.6 323.6 323.8 323.4 323.4 324.1 323.9 323.1 323.9 324.0 323.5 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? __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

September 25, 2011, 12:31 AM	#2
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	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. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

September 25, 2011, 02:15 AM	#3
Kyo Senior Member Join Date: April 14, 2009 Posts: 897	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 __________________ 1. The gun is *always* loaded. 2. Never let the muzzle cover anything you are not willing to destroy. 3. Keep your finger off the trigger unless you are ready to shoot. 4. Be be sure of your target and what is beyond it.

September 25, 2011, 06:26 AM	#5
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	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. __________________ .30-06 Springfield: 100 yrs + and still going strong

September 25, 2011, 09:31 AM	#7
Skadoosh Senior Member Join Date: December 13, 2010 Location: Virginia Beach Posts: 2,016	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. __________________ NRA Life Member USN Retired

September 25, 2011, 04:44 AM	#4
BDS-THR Senior Member Join Date: June 12, 2010 Posts: 479	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.

September 25, 2011, 08:13 AM	#6
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	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.