Case weight

[The Sodbuster]

I weighed some different brands of .223 Remington cases recently.  Listed weights are the average of 6 cases of each brand.  Each case was resized, trimmed to the same length, cleaned, and flash holes deburred.  Results are as follows:

  Brand            Mean weight (in grains)
  R-P                  92.93
  Federal             91.58
  Winchester       87.18
  Military             90.98

The millitary brass was from some Black Hills remanufactured ammo I had.  I had always heard military brass was heavier and with less case capacity than commercial brass.  This wasn't the case (pun intended) with the brass I measured.  I had earlier posted on the topic of .223 and Varget, complaining that I couldn't get near the listed maximum powder charge in my .223 cases.  I was using Remington (R-P) cases.  Maybe if I'd used Winchester I could have easily fit another grain or two of powder in the case. 

I only measured 6 cases and didn't calculate standard deviation or test if sampled weights were significantly different from different brands.

I did this after noticing, while loading for my .308 Win, that my Lapua cases seemed significantly heavier than Winchester brass.

[dave375hh]

Sorting cases by wt. is within the same brand and lot of cases. A light case doesn't nessarily mean you can put more powder in safely. When you change brands or lots you need to work up the loads for those cases. Sorting cases by wt. is only slightly helpful in a rifle that is already benchrest accurate. There are many other "tricks" that will show more inprovment than weighing cases. Experimenting with seating depth, loaded round run out, & different primers are a few. If you want better accuracy you need to load all the same brand & lot of cases. I only sort by wt. for a 6MM-284 that has been blueprinted, rechambered, Cryo'ed, recrowned, restocked, glassed, and had the trigger replaced and adjusted to 1lb. The Norma cases weighed 200gr nominal. I sorted them +/- 0.5 grs. a 1.0 gr spread, or 1/2 of 1%. I got 143 out of 300 cases. The light and heavy cases were sorted into two lots also +/- 0.5gr. The three lots are kept seperate, and any outside of these 3 lots were discarded . I lost 13 for wt & 7 for neck run out.

[ricciardelli]

Case capacity is more important than case weight.

[The Sodbuster]

I don't sort cases by weight.  Maybe I would if I had an electric scale, but it's too much bother on a balance scale.  My point here was that military brass has a reputation for being thicker and with less case capacity than commercial brass.  With the military brass I measured, this was not the case (again, pun intended).

Ricciardelli opined: 

Case capacity is more important than case weight.

Assuming outside case dimensions are nearly identical among different manufacturers (they do have to meet SAAMI spec's, after all), and all cases are trimmed to the same length; then shouldn't lighter cases have more capacity?  Different brass can't vary that much in density. 

I only bring this up because a while back I was loading Varget in .223 Remington cases.  At 2 grains below the maximum my charge was already compressed.  I don't think I could fit another 2 grains in there (I have a long-neck funnel and tap the cases after they're loaded).  Maybe if I'd been using Winchester cases I could have fit more powder in them.  Guess I could always go down to the loading bench and find out.

[PaulS]

Case capacity is more important than case weight.

Case capacity is inversely tied to case weight. If the cases have the same external size the cases that weigh more will have less volume.
For each 6 grains of brass the same volume of 1 grain of powder is taken up.
If you worked up a load using Winchester brass and switched to RP brass in the previous .223 example you would have to reduce the powder charge by 1 grain to maintain the same pressure (all other things being equal). This means in the same gun, at the same temperature and barometric pressure, same bullet, and same powder (including lot#) and only changing from the Winchester case that weighs 87 grains to the RP case that weighs 93 grains. The six grain difference in brass is equal to about 1 grain of double base rifle powder. (the values are different for single base propellents because they are less dense than the double base powders.)

[The Sodbuster]

An addendum to my initial post of 9/02/06:

I recently picked up some once-fired Sellier and Beloit .223 Rem brass.  After resizing, cleaning and trimming I was curious how it compared in weight with other brass.  I couldn't remember my figures from earlier, so I reweighed everything again.  Results are:

Sellier & Beloit     -  96.88 grains/case
Remington         -  93.05 grains/case
Winchester        -  93.01 grains/case
Military               -  91.79 grains/case
Federal              -  91.81 grains/case
W-W Super        -  87.28 grains/case

S&B was the heaviest.  But what I found most surprising was the difference in Winchester and WW Super.  In my previous post, what I called Winchester were actually WW Super cases.  I thought they were identical to Winchester cases.  This time I weighed each type separately and noticed a big difference.  I didn't figure standard deviations and come up with confidence intervals or test for significant differences; but, so much for my preconceived notion about WW Super and Winchester being the same.  Does anyone else have both types of brass in other calibers to compare?

[AtlLaw]

An addendum to my initial post of 9/02/06:

... so much for my preconceived notion about WW Super and Winchester being the same.  Does anyone else have both types of brass in other calibers to compare?

I think I talked about this in another thread or maybe on another forum, but I'm so forgetful in my old age I guess I can say it again.  Someone was asking about weighing brass and weight tolerances and I said I used to sort by weight, but now just do it by headstamp.  I started that because I noticed the same thing you did.  Winchester stamped cases did not weigh, on the average, the same as WW stamped cases.  I also said that I was going to do my own little (not so) scientific test after I developed a good load for a particularly accurate M-700 30/06 I recently picked up.  I've got a ton of 30/06 brass of different manufacture and they all have different average weights as your list shows for the .223.

I'm also using Lake City brass in reloads trying to find an accuracy problem with a friend's H&R Ultra in .308.  It is way heavier then commercial brass and I can't get within 2 gr. of published maximums without high pressure signs.  Night before last, whilst I was happily trimming a batch from my last trip to the range, it dawned on me I had not sorted them ... by year!  So I did.  About 50% were '73, and the rest were a mix of 74, 75, 87, and one lone '69.  I'm going to weigh them when I get home tonight.  Another experiment in the making!
Richard

[AtlLaw]

Okay, weighing all done on the Lake City GI 7.62 brass with these results:
'73 Average 179.4 w/ a 2.8 gr. spread;
'74 Average 179.6 w/ a 2.0 gr. spread;
'75 Average 179.1 w/ a 2.9 gr. spread, and
'87 Average 176.7 w/ a 1.6 gr. spread.
Low vs. high wt. for all cases = 175.5/180.9 for a 5.4 gr. spread
Low vs. high wt. for all cases minus '87 headstamp = 177.9/180.9 for a 3.0 gr. spread

CONCLUSIONS:
a)  I don't have a life.
b)  I need a electronic scale
c)  Lake City brass is pretty consistant by year, within +/- 1.5 gr. from the average
d)  Sorting military brass by year is close enough
e)  the military brass +/- varience is comparable to commercial brass variences, at least with Winchester headstamped 30/06 brass
f)  ergo, sorting commercial brass by headstamp is close enough
g)  this variance (+/- 1.5 gr.) doesn't materially effect group size (based on consistant sub MOA groups fired with preferred handload using Winchester headstamped brass)
h)  therefore, if I ever weigh cases again, my tolerance will be +/- 1.5 gr. from the average... for cases in the 50-60 gr. capacity range, which excludes them itti-bitti .223 cases for my AR match rifle... and my 7x57 is getting close down there, and my 300 Win Mag is way up there, and what about my 45/70?    never mind... 

[beemanbeme]

Okay,  GI 30-06 and .308 cases are indeed heavier.  .223 brass is made to the vender's specs of their commercial brass and only the headstamp is different.  That said, I have never made any allowances for GI .223 brass when working up a load from a load book. (or Steve's pages )

[alsaqr]

Here is a good chart from AR-15 barrels

Link:   http://www.ar15barrels.com/tech.shtml