Brass case weight variance: What's normal?

[ronas]

I have some never loaded IMI 223 brass. I say 223 because the headstamp also says 223 Rem. I bought it in 1993. While it is made by IMI I don't think it would be considered military brass.

I want to handload some rounds for fun to see how accurate a new rifle I have coming might be. I have some 69 grain Nosslers and Sierras FMJBT with no cannalure. I'll be using BLC2 and 748.

To be as consistant as possible I thought it would be good to have brass cases of the same volume so I weighed about 10 cases. The weight varied from 93.1 grain to 95.1 grain for those 10.

So question is:
What should weight variance between 223 brass of same headstamp be?

[joelogic]

I dont know if anyone would know what it should be. But I have seen +/- 5 grains between .223 cases. Maybe someone has some data for accuracy based on case variance. For example, MOA based on cases +/- .1gr and MOA based on cases +/- 5gr. Obviously volume affects pressure but how much does it affect accuracy is the question.

[Corbin Dallas]

I have some never loaded IMI 223 brass. I say 223 because the headstamp also says 223 Rem. I bought it in 1993. While it is made by IMI I don't think it would be considered military brass.

I want to handload some rounds for fun to see how accurate a new rifle I have coming might be. I have some 69 grain Nosslers and Sierras FMJBT with no cannalure. I'll be using BLC2 and 748.

To be as consistant as possible I thought it would be good to have brass cases of the same volume so I weighed about 10 cases. The weight varied from 93.1 grain to 95.1 grain for those 10.

So question is:
What should weight variance between 223 brass of same headstamp be?

If you're looking for bolt action accuracy then you're going about it all wrong.

Brass can vary between brands and amount of times trimmed/shot etc...

The total weight of the cartridge (case, powder, primer, bullet) will have little effect on the accuracy of your rifle.

However, the length, crimp, amount of powder and type of primer WILL have an effect on the accuracy if not done properly.

[Ahhnother8]

The total weight of the cartridge (case, powder, primer, bullet) will have little effect on the accuracy of your rifle.

When ammo was issued at long-range matches, this was the only thing that could be used to quantify ammo, and it makes a huge difference in group size at long-range. Some even sort this way now, with their handloads, for long-range matches.

[swerv512]

for match anmo- all cases should be within 1% of mean weight
everything else i take up to 2.0 sometimes 2.5%

[killshot44]

The two case-types I've run:
PMC: 300 used cases, weights varied from 92.0 to 94.0 grains.
Lapua: 100 new cases, weights varied from 95.1 to 95.9 grains.

2.0gr vs .8gr extreme spead. Won't shoot the latter until Monday but I hope for good things.

With that many PMC cases, I can usually put together groups of 20+ cases with the same exact case weight to try for some uniformity.
It does seem to eliminate the odd flyer (or maybe I'm getting better.....................................haha, riiiiiight).

[Corbin Dallas]

When ammo was issued at long-range matches, this was the only thing that could be used to quantify ammo, and it makes a huge difference in group size at long-range. Some even sort this way now, with their handloads, for long-range matches.

I realize that some people sort their cases like this, but the only thing that could impact the long shot when it comes to overall weight of the cartridge would be the internal volume and the size of the flash hole.

For 223 on a AR15, the overall weight is not going to make a difference. It's not a bench rest bolt gun we're talking about.

[SixPointEight]

I've heard some people say the cases should be within 1%. Others say it should be within .1gr for best accuracy. I have some LC brass that I have sorted by .1 gr, but it's only like 20 in each setup, I might change to 1%, in which case, almost all of them will be in the same pile lol

[Ahhnother8]

I realize that some people sort their cases like this, but the only thing that could impact the long shot when it comes to overall weight of the cartridge would be the internal volume and the size of the flash hole.

For 223 on a AR15, the overall weight is not going to make a difference. It's not a bench rest bolt gun we're talking about.

I will have to disagree with all of the above. Sorting by overall cartridge weight does make a difference. The size of the flash hole has no bearing on things. This has been tested extensively by the benchrest crowd.

The AR's we shoot are VERY accurate. They are not the tacticool, $#!t hanging off them, POS type, commonly seen on the interwebs.

I batch all my brass in 1% groups. For the World Championships in 1/3 of 1% batches. It all matters!!

Lane
2010 Washington State Palma Champion
2010 U.S. F-Class TR National Champion
2009 U.S. Long-Range Team to South Africa
2008 CA State Fullbore Champion
2008 CA State Palma Champion
2007 U.S. Palma Team - shooter
etc...

[Corbin Dallas]

I will have to disagree with all of the above. Sorting by overall cartridge weight does make a difference. The size of the flash hole has no bearing on things. This has been tested extensively by the benchrest crowd.

The AR's we shoot are VERY accurate. They are not the tacticool, $#!t hanging off them, POS type, commonly seen on the interwebs.

I batch all my brass in 1% groups. For the World Championships in 1/3 of 1% batches. It all matters!!

Lane
2010 Washington State Palma Champion
2010 U.S. F-Class TR National Champion
2009 U.S. Long-Range Team to South Africa
2008 CA State Fullbore Champion
2008 CA State Palma Champion
2007 U.S. Palma Team - shooter
etc...

I would like to see these test results because I do not see how the weight of the brass cartridge could have an effect on the accuracy of a bullet.

How does the weight of a fixed object, in a finite amount of space with limited expansion capabilities have an effect on a projectile accelerated from a controlled explosion down a rifled barrel?

Until someone can show me how a stationary object that deviates in weight (not internal volume) can effect a non-stationary object, I have to say "not possible".

[SixPointEight]

same wieght is a rough indicator of volume is all other things are held constant. same lot of brass should have the same alloy, and manufacturing process. is it perfect? no, but less time consuming than using water to measure volume. though, i was doing some reading, and using the same powder charge, one shooter saw a difference of 16fps from higher wieght cases than lower ones. thats less than a half percent of 3000fps.

with that said, my research lead me to this: theres other things that would be more worth yourtime. sort by headstamp, call it good.

[Corbin Dallas]

same wieght is a rough indicator of volume is all other things are held constant. same lot of brass should have the same alloy, and manufacturing process. is it perfect? no, but less time consuming than using water to measure volume. though, i was doing some reading, and using the same powder charge, one shooter saw a difference of 16fps from higher wieght cases than lower ones. thats less than a half percent of 3000fps.

with that said, my research lead me to this: theres other things that would be more worth yourtime. sort by headstamp, call it good.

But that has to do with internal volume. The weight of the case is not the issue here.


For instance, If I made 1 case out of steel and one out of brass and they both have the exact same measurement including internal volume, the heavier weighted case would not make the round more or less accurate.

This is my point.

[SixPointEight]

i understand that, but cases of the same lot will probably be the same alloy. lc doesnt make half brass cases and half steel. like i said, all other things held constant (alloy, outer dimensions, clean vs dirty) a case with higher weight is more likely to have more internal matter, and therefor less volume. its not perfect. checking water volume is a better test, but takes longer.

you are measuring the weight because it implies volume, not because the weight will affect anything. make a case of lead, make one of rice paper. if they hadthe same volume and properties, theyd shoot the same, regardless of weight.

[Ahhnother8]

But that has to do with internal volume. The weight of the case is not the issue here.


For instance, If I made 1 case out of steel and one out of brass and they both have the exact same measurement including internal volume, the heavier weighted case would not make the round more or less accurate.

This is my point.

You are correct, accuracy is not a function of the weight of the case. And you are correct, it is the internal volume that is important, which tends to be correlated with the weight of the brass, hence weight sorting brass. Now the variances in internal volume create differences in velocity, and velocity spreads of 30 fps will show on the target at long range. Many load combinations will have an extreme spread of 30 fps with perfectly matched components, let alone mis-matched ones.

Basically, if you shoot cans at short range, case weight really doesn't matter. If accuracy and/or shot placement is more important, then it is time to start scrutinizing everything more closely.

[Corbin Dallas]

You are correct, accuracy is not a function of the weight of the case. And you are correct, it is the internal volume that is important, which tends to be correlated with the weight of the brass, hence weight sorting brass. Now the variances in internal volume create differences in velocity, and velocity spreads of 30 fps will show on the target at long range. Many load combinations will have an extreme spread of 30 fps with perfectly matched components, let alone mis-matched ones.

Basically, if you shoot cans at short range, case weight really doesn't matter. If accuracy and/or shot placement is more important, then it is time to start scrutinizing everything more closely.

Now that I can understand and I agree. If you're going to sort by case weight then you should do the same for length and weight of each bullet.

Of course, I'm assuming the powder charge is done by weight and not on a standard auto-drop system.