Case weight variation powder capacity and significants on the target

My OCD kicked in today.

A few months ago I weighed 5 of each of several brands of 223 cases. Came up with an average.

As you will see the weight varies from 91.3 to 103.7 grains for the S&B (way out there) so I decided I wanted to know if there was a great difference in powder capacity for these cartridges what I did was I took five ADI cases at 94 grs and weighed them then 5 hornady cases ave 91.4.

I chose to ignore the 3 heaviest esp S&B as they do not seem to be typical.

I filled them all to the top of the neck with AR2208. In addition i used an electric tooth brush to vibrate them to settle the powder. Capacity only varied from 28.0 grs to 28.4 grs!

What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?

Said this many times before. Unless your hotrodding and already near max..nope bugger all at your under three hundy shooting. Under 150 I suggest you would struggle to see any difference. Take heaviest five and lightest five.load them to the same middle of road level,shoot them at hundy and see for yourself.

What you might be more likely to see, is for any given case brand and type (as they tend to have more than one machine stamping out the cases) you will see two three or more distinct groups of cases weights as you weigh up a large enough sample size.

I have been told the some makers of cases keep their cases off each machine together - the match type cases are more likely to have this done.

What I think from my limited experience playing with cases is that the volume or capacity of the case isn't so much of an issue - what I have found is the cases of different batch weights can start to behave differently in terms of not resizing properly/neck tension issues or needing annealing or maybe suffering neck cracking and the like before other batch weights in the same bunch of cases.

That's my gut feeling from my playing - I have had a batch of about 500 milsurp ex-machine gun LC 7.62mm NATO cases, and these separated out into 5 distinct groups by weight. I've used the two biggest batches, one is twice fired and on the third loading is noticeable lighter on neck tension while the other is the same but no issues and still tight. More data required on this as per but that's my observation and thoughts...

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Originally Posted by No.3

What you might be more likely to see, is for any given case brand and type (as they tend to have more than one machine stamping out the cases) you will see two three or more distinct groups of cases weights as you weigh up a large enough sample size.

I have been told the some makers of cases keep their cases off each machine together - the match type cases are more likely to have this done.

What I think from my limited experience playing with cases is that the volume or capacity of the case isn't so much of an issue - what I have found is the cases of different batch weights can start to behave differently in terms of not resizing properly/neck tension issues or needing annealing or maybe suffering neck cracking and the like before other batch weights in the same bunch of cases.

That's my gut feeling from my playing - I have had a batch of about 500 milsurp ex-machine gun LC 7.62mm NATO cases, and these separated out into 5 distinct groups by weight. I've used the two biggest batches, one is twice fired and on the third loading is noticeable lighter on neck tension while the other is the same but no issues and still tight. More data required on this as per but that's my observation and thoughts...

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Very interesting comments.

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Originally Posted by Micky Duck

Said this many times before. Unless your hotrodding and already near max..nope bugger all at your under three hundy shooting. Under 150 I suggest you would struggle to see any difference. Take heaviest five and lightest five.load them to the same middle of road level,shoot them at hundy and see for yourself.

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My thoughts too. Rare I shoot over 150yards.

Ummm, might do that test, but will be sometime ime afraid.

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Originally Posted by Oldbloke

My OCD kicked in today.

A few months ago I weighed 5 of each of several brands of 223 cases. Came up with an average.

As you will see the weight varies from 91.3 to 103.7 grains for the S&B (way out there) so I decided I wanted to know if there was a great difference in powder capacity for these cartridges what I did was I took five ADI cases at 94 grs and weighed them then 5 hornady cases ave 91.4.

I chose to ignore the 3 heaviest esp S&B as they do not seem to be typical.

I filled them all to the top of the neck with AR2208. In addition i used an electric tooth brush to vibrate them to settle the powder. Capacity only varied from 28.0 grs to 28.4 grs!

What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?

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It certainly not OCD (and I am a card carrying member of this group) to wonder how variables in components effect velocity and point of impact. Long ago I found that in my .308 I found that one additional grain of powder raised the point grain of powder raised the point of impact by around 1 inch at 100 yards. Later I found it also increased velocity by around 50 fps. Lighter projectiles also shot higher than the heavy ones. A heavier case will give more velocity than a lighter one but how much? Frankly I don't know. I have actually loaded cartridges for the .223 and .308 to test this but due to sloth are yet to shoot them. I do know from experience that results vary from cartridge to cartridge and also from rifle to rifle with the same cartridge. Will post more after shooting.
Grandpamac.

Case weight variation isn't necessarily correlated to capacity. The extractor cut and variation thereof contributes significantly

What about the effect on the brass, smaller internal capacity would equal more pressure than the larger capacity? Amounting to shorter case life or is the difference in pressure in this instance insignificant. I'm nothing close to expert or experienced enough to know. Just my thought process

I suspect there’s more to consider than just weight difference between brands as a proxy for case capacity. There maybe differences in brass composition, leading to harder or softer brass, neck tension or splitting, annealing properties, etc. The distribution of brass within the case design might also differ slightly eg thicker brass in head vs body.
I have had one example where brass weight worked out as a fairly good proxy for capacity. In 65.06ai I was working up loads for 140 AMAX with RL25. Norma brass (182-183 gn) vs RP brass (195-197gn). The RP load was giving 2920-30 fps vs Norma load at +1.5gn gave 2970fps. In both cases the load was just below max pressure as judged by ladders run previously.

If brass / case manufacturers used a standard mix across the board there may be some validity to case weight variations, but as said extractor grooves are even different, the only way to see a difference in capacity is measure cases internal volume, with a fluid that fills every part of the combustion chamber ( for that is what it is). using powder has an inherant issue in that the grains will never stack the same. Shooting at short distances will show hardly any difference its when you get past 600 yds and further you see the difference in case volume showing up as erratic velocities which at distance will show as vertical dispersion.
I suspect but have never tested if you took a Winchester case and an ADI case. That had been fired in the same rifle several times and had completely achieved their true internal volume. Then prepared them with the same charge and primer and projectile and then fired them over a chronograph or printed them on paper at distance, you would then see the difference.

My calculations using a band of 2 grains differnce in each cases capacity shows the smaller capacity case would have a higher pressure and higher velocity.
Using a .308 as my base test pressure goes from 54290 to 59600 thats over 5000 psi!! and the velocity change is a mere 40 fps so would not proove much at 100 yds but at 1000 is ? (didnt get there in calculus).

Any ways thats the difference i dont want... the extra pressure. And yes Micky I am talking about hotrod loads.
For example if I have worked up my loads in Winchester cases and then an ADI case gets in the mix now know I could expect to bump pressure up by 5000 psi, with no other variables altered.

"the only way to see a difference in capacity is measure cases internal volume, with a fluid that fills every part of the combustion chamber ( for that is what it is). using powder has an inherant issue in that the grains will never stack the same"

Perhaps this is true, I've read it many times.

But we fill cases with powder, not water so, seems more relevant to me. In any case settling the powder with a vibration will minimise any variables.

Could fill the cases for comparison of volume with a fine grain powder (which flows like water).

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Originally Posted by rupert

Could fill the cases for comparison of volume with a fine grain powder (which flows like water).

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Yes, I could have used AS50N which is a fairly fine shotgun powder. But, honestly, I use AS2208 in the 223 I want to know how much AS2208 they hold, not water.

If I had a container used to store biscuits and I wanted to know it's capacity, would I use water. Nope that would be useless, because of the shape and size of the biscuits. Because I need to know how many biscuits it holds. I understand it's different but, really!

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Originally Posted by Oldbloke

Yes, I could have used AS50N which is a fairly fine shotgun powder. But, honestly, I use AS2208 in the 223 I want to know how much AS2208 they hold, not water.

If I had a container used to store biscuits and I wanted to know it's capacity, would I use water. Nope that would be useless, because of the shape and size of the biscuits. Because I need to know how many biscuits it holds. I understand it's different but, really!

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Considering your looking for ballistic differences on target then you need to measure the metric that has the greater effect. Which is true combustion chamber size, of which the combustion gases rapidly fill and of which will then determine pressure that the projectile is subjected to.
Powder volume for the same powder will have a lesser effect than the combustion volume on pressure.

If you werent going to fire the round for an on target effect then your technique would work adequately, but still not be as good as getting a truer volume demension using a more consistent medium.

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Originally Posted by johnd

..
I suspect but have never tested if you took a Winchester case and an ADI case. .....
My calculations using a band of 2 grains differnce in each cases capacity shows the smaller capacity case would have a higher pressure and higher velocity.
Using a .308 as my base test pressure goes from 54290 to 59600 thats over 5000 psi!! ..
..

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That is a well known difference with older NRA shooters. Commercial Win brass had a much higher capacity than mil brass. Using the same warm load from a Win case in the mil brass would produce much higher pressure. It wasn't subtle.

As John said above, slight differences are often imperceptible on game targets out to 300yds but count for a lot past 600yds.

Many factors could come into the variation in case weight before an observable difference in case volume becomes obvious - as I mentioned earlier the average plant producing cases will have a lot more than one machine producing a type of case to get the volume they need to fill orders. Mil brass especially (going back to my Lake City milsurp experience).

It would not take much of a difference in punch and die set ups to create a minute difference in case head thickness, each machine would have a different roll of feedstock metal that is being made into the cases (slight difference in metal composition will give you a different density of metal), and the extractor groove cut and rim chamfer would all play a part in this. The main thing here is one grain of metal is a hell of a lot less than one grain of powder so you might be able to see a big difference in batch weight of cases without seeing a large difference in internal volume.

What that could do is give you cases which resize and age differently than others as the factors that can change if cases are coming off different machines include things like different annealing cycles so you are starting with different hardness and ductility in amongst your batch of cases giving you different neck tension and different obturation and springback amounts potentially.

We can't really control this though, and most people I think would not be using big enough sample sizes to get a handle on if there are weight groups in the batch of cases - about 500 of the LC milsurp cases showed 5 distinct groups where the case weight was within 2gr in the batch, but there were if I remember right something like 4 or 5 grains at least between batches. It was noticeable at any rate (all cases cleaned, trimmed and resized with the primer pocket uniformed/decrimped prior to weighing).

My main point is internal volume is only one thing that might affect case performance.

"What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?"

To clarify out to 200 yards.

I had a load using winchester brass that would shoot .4 of an inch at 100 meters, I have duplicated this load in about 4 different types of brass and they all shoot fine. I don't notice any difference.

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Originally Posted by Oldbloke

"What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?"

To clarify out to 200 yards.

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If by "significantly", you mean "to a point where it would be meaningfully detrimental to hit probability for hunting purposes out to 200 metres"

The answer is that I'm highly confident that it absolutely would not matter in the slightest.

E: I might test this though as I've got a dozen different types of .223 brass, maybe I'll load a 10rd group with 1 type, then a 10rd group with 10 different types - and see what it looks like on paper.

E2: It may present a risk of exceeding maximum SAAMI (or CIP) pressures in some of the cases, in some circumstances. The real safety risk of this is highly variable.

The obvious advance to this line of thought, is to actually go and do some shooting and test it.

edit: As Gimp has suggested. The obvious comparison would be between commercial and military.

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Originally Posted by Oldbloke

"What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?"

To clarify out to 200 yards.

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Greetings,
Yes some of us had abandoned the original question and headed down into the rabbit warren. To address your questions and from my experience with the .223 the difference is unlikely to be significant out to 200 yards. The difference between the 55 grain Hornady in my .223 fired at 110 metres at velocities of around 2,700 fps and 3,150 fps was only 30mm. Velocity differences due to case make would be significantly less than that.
Regards Grandpamac.

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Originally Posted by gimp

If by "significantly", you mean "to a point where it would be meaningfully detrimental to hit probability for hunting purposes out to 200 metres"

The answer is that I'm highly confident that it absolutely would not matter in the slightest.

E: I might test this though as I've got a dozen different types of .223 brass, maybe I'll load a 10rd group with 1 type, then a 10rd group with 10 different types - and see what it looks like on paper.

E2: It may present a risk of exceeding maximum SAAMI (or CIP) pressures in some of the cases, in some circumstances. The real safety risk of this is highly variable.

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Yep. most of my experience with mixed brass has been little effect. But I had one memorable occasion where a mate changed brass brands without checking load and ended up with blown primers and a popped mag floor plate.
Though to be fair we were young and he might have been pushing pressures with his original load.
it did lead me to never mix brass too this day however.

So again using the milsurp brass example, there's over 20 grains of weight difference between the lightest batch of cases and heaviest batch of cases. Comparing to the sporting cases I have on hand, they all fall into a similar range there's maybe a few lighter than the lightest of the milsurp and a few in the middle but I was comparing a small sample size of one of each case on the digital scale.

Basically I haven't found anything that's a big jump of like 50gr difference anyway. Most of the cases for the dimensions that are easy to check are pretty much within cooey of each other. I don't have many other milsurp .308/7.62 NATO cases to really compare to, but I'm not seeing a massive variation in case weight or a massively obvious difference in case volume (given that not all of them a cleaned, trimmed to length so I'm not starting from a 'point' either).

Using the same powder charge in the milsurp cases, they group the same despite the batch weight variations - and any variation in speed between batches is lost in the noise (I can't pick it anyway).

I'm fairly confident to suggest that I don't think that you would see much of a variation in terms of POI changes from simply changing cases, there may be some brands out there in some calibers that have a noticeable weight difference compared to the .308 cases that I was playing with that have significant enough differences to cause issues though. I would not think that you'd want to be mixing cases for target shooting or somewhere where you need to be able to have maximum confidence in your setup, but for average hunting purposes with .308 I haven't seen anything significant in what I've checked that would cause a problem in terms of velocity variation.

I still don't think it's advisable in terms of brass life and quality control to be running mixed brass - just from what I observed with the two batched weights of milsurp brass (I keep these separate in 50-round plastic boxes - same load, same treatment just the cases aren't mixed).

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Originally Posted by Oldbloke

"What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?"

To clarify out to 200 yards.

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Thanks for adding the 200 yard limit to your original post @old bloke as you have already noted (and we all agree) it wont make any difference on the target. Wether you measure with biscuits or bullshit the pressure change is real though. Dont shoot the messenger, we are on a public forum where infornation dished out can be used by some that may not fully comprehend the results.

Yep, that is fair too. If you are running to the absolute limit for the safety of the components and rifle you are using, you'd be a brave operator to start swapping any components out without starting low and working back up to verify all is still OK.

I think another fair point, is that doing this exercise with something like a small .22 round would probably yield somewhat different results to a .338 barbeque-em-at-600 cannon.

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Originally Posted by Oldbloke

"What are people's opinions?

Would mixing cases:

Change group size significantly?

Change point of impact significantly?"

To clarify out to 200 yards.

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Nope AS LONG as your load isn't hotrodding to begin with. It could also depends on rifle and more so on what you consider significant. I once fired 8?10? different .270 loads into same target at hundy yards...wasn't my best day of shooting and was flinching badly by day's end( before suppressors) but that multi shot,multi bullet weight group was able to be covered by a playing card.

Ummm, for further clarification.
Load is:
24.7 AR2208
55gr Sierra Superoo. 1365 game king.
It's very mild.

Sorry should have provided more info in the OP.

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Originally Posted by grandpamac

Greetings,
Yes some of us had abandoned the original question and headed down into the rabbit warren. To address your questions and from my experience with the .223 the difference is unlikely to be significant out to 200 yards. The difference between the 55 grain Hornady in my .223 fired at 110 metres at velocities of around 2,700 fps and 3,150 fps was only 30mm. Velocity differences due to case make would be significantly less than that.
Regards Grandpamac.

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Thx. Good info.

Firstly throw those S&B cases as far away as you can. They are junk.*You would get better returns with annealing and improving neck geometry and tension for the best release. 2C.

One case (1000 rounds) of 223 I got had 4x different head stamped cases. Originally started sorting according to head stamp but the reality was they all shot to near enough same poi at 200 yards, good enough for goats, pigs, deer. Other cases of 1000 rounds have had two or three different head stamps, all close enough regarding poi to go hunting. I have a few kgs of 223 brass, about 9x different brands/head stamps. Like MD I’ve shot 10-15 rounds of mixed loads out to 300 yards at rifle range and got groups good enough for hunting with 223. Done similar at 600 yards, mixed cases and powder weights (1-1.5 grains), with 6.5 CM and ended up with groups that would have been a dead animal each shot. The only time I separate into separate lots, after checking water volume per head stamp batch, is when loading for specific long range loads or range competition. I think that sometimes we get too hung up on minor details instead of settling on a load, not hot-rodded, and getting out there shoot shit. Case weight means jack shit when it comes to comparing head stamps/ case volume. Just my observations.

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Originally Posted by TeRei

Firstly throw those S&B cases as far away as you can. They are junk.*You would get better returns with annealing and improving neck geometry and tension for the best release. 2C.

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Yes, think I will do that. They really are waaayyy heavier.

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Originally Posted by Oldbloke

Yes, I could have used AS50N which is a fairly fine shotgun powder. But, honestly, I use AS2208 in the 223 I want to know how much AS2208 they hold, not water.

If I had a container used to store biscuits and I wanted to know it's capacity, would I use water. Nope that would be useless, because of the shape and size of the biscuits. Because I need to know how many biscuits it holds. I understand it's different but, really!

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True but depending on how your biscuits pack into the tin there could be between 26 and 50 percent empty space between them. Same with firewood if you have to buy it heaven forbid it's sold as a thrown meter pack it properly and you're lucky to get over half that. Same with powder. If you were to repeat your results several times for each case I suspect you will get a range of results that measure usable capacity, but the only true measure of the cases capacity is to use liquid.

Video from MDT. Maybe a bit simplistic and not a large enough sample size to satisfy some on here but gives food for thought on another ammo aspect that some individuals may get too hung up about. Brings back memories of clipping ends off .303 fmj ammo back in the day, worked well enough at short/medium range. Something to think about. Have at it.
https://youtu.be/svzsT3SYFXM?si=b1Y0eCoUUM5gbv2d

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Originally Posted by Oldbloke

Yes, think I will do that. They really are waaayyy heavier.

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Yep, done. Only 40.