Weighing Brass

[Rick Ratzlaff]

I was handed a project. A hunting rifle we'd like to get to 1 MOA. Might be a streach, but...
A pile of brass and components for a 25-06. So starting from scratch and curiosity i decided to weigh some brass.

FC Nickle plated. Out of 34 cases I had a 16.3 GN difference.

9 cases were within 2 gn's, then the rest dropped fully 10 grns.

I'm surprised and think this is extreme. Looking for comments.

 

[Ned Ludd]

What is the origin of the brass? Your description, "pile of brass" could mean a large amount of virgin brass all from the same lot, a big pile of fired brass accumulated from one or more of your friends rifles over time, or even a big pile of cases picked up at the range. A 16.3 gr spread is in the ballpark of 10%. That would be pretty bad for virgin brass out of the same lot, but not unexpected for a pile of brass accumulated from several different lots. Did you actually check the internal volume of any of these cases? I'd be more curious to know how much that varied.

 

[savagedasher]

You don't care what the brass weigh
Internal volume difference is all that matters .
Larry

 

[Rick Ratzlaff]

Sorry - their all once fired factory. All one box and part of another.

 

[zipollini]

When I weigh sort my 6XC Norma match brass I try and sort to .1grain and group into groups with a spread of no more than .5grains.

 

[bozo699]

Rusty,
First for a hunting load unless planning on long range I wouldnt worry too much however I like my expensive loading dies to much to put nickle brass through them. With some H-4831 and some 120 grain bullets and a rifle with a properly fitting stock and a tuned trigger, properly mounted good piece of glass you should have no problem achieving a 1" rifle
Wayne

 

[jimbires]

I agree with Larry above as far as weighing brass goes . brass weight means nothing , it's the water capacity you should be concerned with . the other night I was checking a few to get an idea where I was at here is the results . these are 3 times fired with only a neck size in between loadings, so the brass should be fully expanded .


case ..........empty ....... .... full........ ..... water capacity

1..............240.34 ..............325.44.................85.10
2 .............235.04...............320.28.................85.24
3..............236.64...............321.82.................85.18
4..............237.02...............322.58.................85.56
5..............236.20...............321.62.................85.42

 

[Auto-X Fil]

I was handed a project. A hunting rifle we'd like to get to 1 MOA. Might be a streach, but...
A pile of brass and components for a 25-06. So starting from scratch and curiosity i decided to weigh some brass.

FC Nickle plated. Out of 34 cases I had a 16.3 GN difference.

9 cases were within 2 gn's, then the rest dropped fully 10 grns.

I'm surprised and think this is extreme. Looking for comments.

This is a complete waste of time. Brass sorting is done to reduce velocity variation for long-range shooting, and also in short-range BR because everything has to be tweaked to a gnat's patootie there.

It will have zero difference in a hunting gun. Shoot good bullets, work up a load intelligently, prep the brass properly. If that fails, check the crown and the bedding.

If load development was done with a method like OCW, you can throw powder with a measure and have +/- 0.5gr variation without any detriment to accuracy within 300yd.

 

[Langey]

case ..........empty ....... .... full........ ..... water capacity

1..............240.34 ..............325.44.................85.10
2 .............235.04...............320.28.................85.24
3..............236.64...............321.82.................85.18
4..............237.02...............322.58.................85.56
5..............236.20...............321.62.................85.42

Here are the results in a graph:

 

[XBBR Shooter]

You don't care what the brass weigh
Internal volume difference is all that matters .
Larry

But internal volume (when firing) is solely determined by the case weight.

Measuring case volume with water is rife with errors.

Take a new case, put in a fired primer. Weigh it.
Fill it with water, weigh it, get the difference. OK?

Now fire it and do thee same.

Now fire it again and do the same.

Now fire it again, and do the same.

Try annealing the neck and shoulder and do the above again.

Each time you will get a different weight (ie "volume").
But the real volume doesn't change, the shape of the case, and the spring back, change with each firing.

Water volume means nothing unless you can constrain the case body to be the same each time... like running in a body or FL die, then fillinng it with water (while still in the die)... if not, you are just blowing smoke (up you know where).

 

[pemo]

When I tested if my 243W hunting rifle was picky regarding case weight I found a strong correlation between Case weight (Y-axis) and case volume (X-axis).

The slope of the trendline indicates a brass density of 8.3 g/cc.

 

[XBBR Shooter]

I was handed a project. A hunting rifle we'd like to get to 1 MOA. Might be a streach, but...
A pile of brass and components for a 25-06. So starting from scratch and curiosity i decided to weigh some brass.

FC Nickle plated. Out of 34 cases I had a 16.3 GN difference.

9 cases were within 2 gn's, then the rest dropped fully 10 grns.

I'm surprised and think this is extreme. Looking for comments.

To your original question...

1 - Last year, I resurrected my 222 Mag bench rifle from the back of the safe. I cleaned and annealed all the brass I had accumulated over the years, to bring them all down to a base line starting point. I weighed all my brass, over 900 pieces of Remington (brand) 222 Mag cases and the extreme spread was 1.9 grains (which shocked me). The rifle still shoots in the mid 1's.

2 - Many years ago, I had (and still have) a 308 calibre match rifle that shot in the mid to high 0.2's with a batch of 100 pcs of Fed match cases. The cases weighed an average of ~176 with a ES of 3 grains. I bought another 100 pieces of the same brass, and groups went to ~0.7". I could not figure out why. After checking all the usual suspects, I checked the weight of the cases (now all mixed up). The weight range went from 154 to 177.... when I separated the cases by weight, I had 108 pieces in the original weight group, the rest varied from 154 to 174, and were all over the place.
When I shot loads with the original weights - the groups came back to where they were supposed to be. I contacted Federal, and they flipped me the bird, so I never bought Fed brass again.

So, in my mind, case volume DOES matter, if your rifle is capable of shooting well, and case volume is best determined by case weight.

 

[MagnumManiac]

Hate to burst your bubble, but, after extensive testing on correlation of brass weight and ACTUAL measured volume, there simply isn't an accurate correlation.
Some brass that weighs higher or lower can have vastly different volumes, as one would expect, but, in actually sorting brass by volume on FIRED cases with a new primer inserted upside down, my shooting partner and I found that some cases that were HEAVIER, had the same volume as cases 5gr-8gr lighter.

Ever had a flyer with a case that weighed the same as the others?
I bet if you measured all of their volumes, there would be quite a few discrepancies.
My Lapua brass in 300WM I use for 1000yrd F-Class all weigh very similar, no more than a 1gr spread, but, the volume on those have shown a .5gr swing, this is enough to show up vertical at 1000yrds.

Cheers.

 

[XBBR Shooter]

You can't burst my bubble - unless you are filling the cases when they are restrained by a body or FL die - you are kidding yourself.

Look at Pemo's graph above my post...

The volume that we are concerned with, is not the static case volume, but the volume when the case is under pressure, and forced against a fixed container (the chamber walls).... otherwise, you are just measuring the variances in cases' state of relaxation.

 

[jlow]

I agree with Larry above as far as weighing brass goes . brass weight means nothing , it's the water capacity you should be concerned with . the other night I was checking a few to get an idea where I was at here is the results . these are 3 times fired with only a neck size in between loadings, so the brass should be fully expanded .


case ..........empty ....... .... full........ ..... water capacity

1..............240.34 ..............325.44.................85.10
2 .............235.04...............320.28.................85.24
3..............236.64...............321.82.................85.18
4..............237.02...............322.58.................85.56
5..............236.20...............321.62.................85.42

There is a slight complexity when doing what you are doing and trying to get a correlation that most people do not realize.

The best time to try to get a weight to volume correlation is when the brass is new. If you used fired brass, especially 3 times fired brass, if the charge you use in all three firing is different, the case will swell to different degree and no amount of sizing will bring it back because of difference in work hardening - we don't anneal the head. So when the degree of swelling is different, their volume no long correlates to weight which is what you are seeing.

 

[Mozella]

............ snip.......
Each time you will get a different weight (ie "volume").
But the real volume doesn't change, the shape of the case, and the spring back, change with each firing.
........... snip..........

Did you misspeak? Unless you're testing in a freezer, the weight of water and the volume of water are essentially interchangeable; i.e. since it's easy to measure water weight, you can use that to compare relative case volume rather than measure the actual volume because volume is so much more difficult for must of us to measure.

So if the "real volume" doesn't change, then the actual shape of the case doesn't matter. A tall skinny 750 ml bottle of Bordeaux contains the same volume of wine as does a 750 ml bottle of Pinot Noir, even though the Pinot Noir is short and fat.

Or, perhaps I misunderstood what you are saying. I won't argue the fact that a fireformed case may be a different volume than a resized case, but if two cases have the same volume but different shapes, then the question of volume is self evident. Did I miss something?

 

[MAGNETISCH]

You don't care what the brass weigh
Internal volume difference is all that matters .
Larry

I care more about internal volume capacity similarities.

 

[wapiti25]

MagnumM where did you buy 300WM Lapua brass?

 

[XBBR Shooter]

"[snip].......
Each time you will get a different weight (ie "volume").
But the real volume doesn't change, the shape of the case, and the spring back, change with each firing.
.... [snip]"

Did you misspeak? Unless you're testing in a freezer, the weight of water and the volume of water are essentially interchangeable; i.e. since it's easy to measure water weight, you can use that to compare relative case volume rather than measure the actual volume because volume is so much more difficult for must of us to measure.

So if the "real volume" doesn't change, then the actual shape of the case doesn't matter. A tall skinny 750 ml bottle of Bordeaux contains the same volume of wine as does a 750 ml bottle of Pinot Noir, even though the Pinot Noir is short and fat.

Or, perhaps I misunderstood what you are saying. I won't argue the fact that a fireformed case may be a different volume than a resized case, but if two cases have the same volume but different shapes, then the question of volume is self evident. Did I miss something?

I do not see what is so hard to understand.

1 - Metal cases (or other things) of the same alloy, even with different shapes, will displace the same amount of volume. (Archimedes, 300 B.C.) who has never been wrong.
2 - The case(s) will vary in shape and "free standing volume".
3 - So the measured water will vary too.
4 - But we are interested in the case volume under pressure.
5 - So measuring cases by filling then with water, will vary, depending on several variables.
6 - To be accurate in using water, you must constrain the case body in a uniform (and repeatable) space.
7 - That means in a Full Size die, or a Body Die, where all the cases are held in the same size "girdle".

... or, you can weigh the case(s).... if the case weighs the same as others, and is put in a chamber under a bunch of pressure, then the inside space will have the same volume, even if it's distribution varies

 

[pemo]

Just to clarify. I have measured volume after firing with spent primer in place, using this method: http://forum.accurateshooter.com/threads/case-volume-determination-pic-heavy.3896148/

Measured velocities also show strong correlation with case- weight & volume, see below.

243Win
X-axis: Case volume, grains water
Y-axis: muzzle velocity, 5m from muzzle, meters per sec