Rifle case weight vs volume
- Thread starter BJung
- Start date
Nope. It's not worth the time and effort to separate cases or to weigh 'em.
The BR guys do that kind if thing regularly, but the rest of us won't see any improvement. The BR guys, who we owe a great deal to(there'd be no plethora of match grade bullets without them), aren't like the rest of us. Nor is their equipment.
The BR guys do that kind if thing regularly, but the rest of us won't see any improvement. The BR guys, who we owe a great deal to(there'd be no plethora of match grade bullets without them), aren't like the rest of us. Nor is their equipment.
weight differences will not correlate to volume differences due to the brass thickness in the web and case walls. One winter a couple of years back and weighed out 100 cases then did the volume measurements. My conclusion was weight differences will not correlate to volume differences due to the brass thickness in the web and case walls.
As far as volumetric differences think about the volume of the case and the barrel and pressure difference caused by a difference of a cc or two when dealing with thousands of pounds of pressure.
If you really are into accuracy and want something to do on a cold winter night buy a box of 500 bullets then sort them by base of the bullet to ogive measurement. That will relate directly to case volume and more consistent seating. I find I get significantly fewer flyers, a difference of .002 to .003 between 3 - 5 bullets really can be seen on paper even at close range with a accurate rifle and good technique
As far as volumetric differences think about the volume of the case and the barrel and pressure difference caused by a difference of a cc or two when dealing with thousands of pounds of pressure.
If you really are into accuracy and want something to do on a cold winter night buy a box of 500 bullets then sort them by base of the bullet to ogive measurement. That will relate directly to case volume and more consistent seating. I find I get significantly fewer flyers, a difference of .002 to .003 between 3 - 5 bullets really can be seen on paper even at close range with a accurate rifle and good technique
Sorting by headstamp and year can be helpful from the standpoint of load history and age tracking. You'll find some brass starts splitting sooner than other headstamps, for example, so if you start getting splits and they are all among the brass with the same headstamp and you acquired that brass all at once, then it is probably time to consider scrapping it or to get into neck annealing and reaming donuts.
Not needed until your biggest 10 shot groups at 100 yards are one third inch. Then sort into one grain weight spread increments. Case volume uniformity is way, way down on the list of things needed for best accuracy.
When the outside dimensions of the cases of a lot are all the same, heavier ones will have less volume than lighter ones.
When the outside dimensions of the cases of a lot are all the same, heavier ones will have less volume than lighter ones.
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Weight of the case because the more out of round (oval or egg shaped) the case inside body is, the less space there is. Less room for filler.
Maybe I explained what I want to do incorrectly. I was going to weigh a case as a tare weight and then add Cream of Wheat with the case to determine the weight of the filler.. One thread on another sights says that they fill a case will rubbing alcohol "with" the spent primer. I would be concerned about the primer because of weight variations. A 21st Century primer plug or something like that found in a hardware store might be better, I think. You reminded me about the oval egg effect. I'll look it up.
best contact AAA and get a map book of the rabbit hole 
just kidding, been there and done that myself as have plenty of others. It is a great way to kill a few winter evenings
Accurate Shooter Forums has several good threads on this subject. This is something that was in vogue with long range benchrest shooters and extreme long shooters awhile back. Lots of good statistics over there. Here is one https://forum.accurateshooter.com/threads/measuring-case-internal-volume.3807241/
Also are you going to be buying a Sartorius Entris or other scale capable of .0001 gram resolution to measure your powder charges. A&D 120's are only .001 resolution scales and can't go that fine on their resolution. https://balance.balances.com/scales/1223
Then you can mark each case and adjust the powder charge by a kernel or two to match differing case volumes. You might even consider cutting powder kernels in half to get it exact. Well that might be going a step too far, but always something to consider when you can start seeing a difference that fine on paper
just kidding, been there and done that myself as have plenty of others. It is a great way to kill a few winter eveningsAccurate Shooter Forums has several good threads on this subject. This is something that was in vogue with long range benchrest shooters and extreme long shooters awhile back. Lots of good statistics over there. Here is one https://forum.accurateshooter.com/threads/measuring-case-internal-volume.3807241/
Also are you going to be buying a Sartorius Entris or other scale capable of .0001 gram resolution to measure your powder charges. A&D 120's are only .001 resolution scales and can't go that fine on their resolution. https://balance.balances.com/scales/1223
Then you can mark each case and adjust the powder charge by a kernel or two to match differing case volumes. You might even consider cutting powder kernels in half to get it exact. Well that might be going a step too far, but always something to consider when you can start seeing a difference that fine on paper
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I generally sort by headstamp and with GI brass headstamp and year. Does it really matter much? I doubt it. A few years back I sized and trimmed 50 cases in lots of ten. The case outside dimensions were as uniform as I could get them. Sadly I have yet to load them and see what I get both over my chronograph and how they group for me.
I used a small bit of modeling clay to seal the primer pockets, the same clay we use in bedding. That is what shows on the data sheet as a "tare". There are 5 different case manufacturers and I regret not including Lapua brass as I had some brand new when I did this.
I used distilled pure water but the reality is tap water would likely have done as well. I omitted primers totally. Primer pockets were all brushed clean. The brass was just randomly yanked from stuff I had on hand.
Hopefully come next spring / summer I can get these cases loaded and out to the range. I doubt that off the bench at 100 yards I'll see much difference but will see how it plays out. On the bright side I just mailed in my 2021 range fees.
Ron
I used a small bit of modeling clay to seal the primer pockets, the same clay we use in bedding. That is what shows on the data sheet as a "tare". There are 5 different case manufacturers and I regret not including Lapua brass as I had some brand new when I did this.
I used distilled pure water but the reality is tap water would likely have done as well. I omitted primers totally. Primer pockets were all brushed clean. The brass was just randomly yanked from stuff I had on hand.
Hopefully come next spring / summer I can get these cases loaded and out to the range. I doubt that off the bench at 100 yards I'll see much difference but will see how it plays out. On the bright side I just mailed in my 2021 range fees.
Ron
The ratio of weight change to volume is not 1 to 1.
I have cross checked some cases using fine ball powder as a realistic method vs water which is not how we load powder.
Real world its even less that the figures above.
I will take Bart B word on it, I don't' shoot that well most of the time and never consistently so all I do is go with mfg and not worry about variation within mfg.
I have cross checked some cases using fine ball powder as a realistic method vs water which is not how we load powder.
Real world its even less that the figures above.
I will take Bart B word on it, I don't' shoot that well most of the time and never consistently so all I do is go with mfg and not worry about variation within mfg.
Being as the outside dimensions are the same (or as close as we can get them) there are only two things that will affect the weight of the case.
Thickness of the brass, and its density. Cartridge brass is not 100% identical maker to maker and there are also variances lot to lot.
Given its the same outside the heavier case must either be thicker (which affects volume) or made of a more dense material (which may not affect volume). Could even be both together.
We can do very precise measurements many ways, and they are useful for showing general trends, and the specifics of what was measured.
HOWEVER, there is no guarantee that the brass in your hands will be identical to what was tested & measured. SO, don't take the fine details as holy writ.
Your stuff should be very similar. It might even line up perfectly with someone else's test data. But don't assume that, do your own measurement on what you have. That's the only real values you need to be concerned with.
Thickness of the brass, and its density. Cartridge brass is not 100% identical maker to maker and there are also variances lot to lot.
Given its the same outside the heavier case must either be thicker (which affects volume) or made of a more dense material (which may not affect volume). Could even be both together.
We can do very precise measurements many ways, and they are useful for showing general trends, and the specifics of what was measured.
HOWEVER, there is no guarantee that the brass in your hands will be identical to what was tested & measured. SO, don't take the fine details as holy writ.
Your stuff should be very similar. It might even line up perfectly with someone else's test data. But don't assume that, do your own measurement on what you have. That's the only real values you need to be concerned with.
All the ammo component tolerances at minimum numbers don't matter if the other two parts of the system are not as refined.
The first mass produced batch of 308 ammo with Sierra 155 grain HPMK bullets had new unprepped 173 +/- 2.5 grain Winchester cases, Federal primers, 45.3 +/- .2 grains of IMR4895 and bullets seated with up to .0035" runout. 20 shot tests at 600 yards printed under 3 inches in several rifles shot by several people.
The first mass produced batch of 308 ammo with Sierra 155 grain HPMK bullets had new unprepped 173 +/- 2.5 grain Winchester cases, Federal primers, 45.3 +/- .2 grains of IMR4895 and bullets seated with up to .0035" runout. 20 shot tests at 600 yards printed under 3 inches in several rifles shot by several people.
I've mostly found threads about how to measure case volume but nothing definitive comparing loads made with cases based on case volume vs case weight vs just case head stamp. I've been weighing my range brass with the same head stamp and choosing cases that fall among the majority with the same weight. But, does volume matter at all??? So far I've read some long-range shooters uses weighed brass. Others use volume? So, what's at the end of the rabbit hole?
what I found was a pile of time and money wasted on stuff that did not matter. Now I spend my money on ammo, good barrels, and smooth triggers and my time practicing at the range in windy conditions and dry firing at home. You know, the kind of stuff that will actually help with accuracy
What else did you find out? Are you still weighing and grouping your brass? I can relate to the kernels.. I'd use my trickler and balance and expect the pointer to line up with just one more kernel then, plot, one more and it's over the line! Practice is important. Unfortunately, most of my time is testing and chasing for the ideal petloads for my guns first.
Extremely uniform cases and powder charges are not near the top of the list of requirements for best accuracy.
The first requirements are barrel groove diameter needs to be at least a few ten-thousandths inch smaller than the bullet's diameter and have very uniform bore/groove diameters and rifling twist.
Barrels should be totally free floating and fit to receivers whose face is squared up so they shoot to point of aim while they heat up.
The first requirements are barrel groove diameter needs to be at least a few ten-thousandths inch smaller than the bullet's diameter and have very uniform bore/groove diameters and rifling twist.
Barrels should be totally free floating and fit to receivers whose face is squared up so they shoot to point of aim while they heat up.
When I posted the data I posted in Post #11 my efforts were more a matter of curiosity and to dispel a few myths for myself. I am in the group who believes a better quality barrel and trigger contribute more to accuracy, and obviously practice than case capacity. However with that in mind the thread is about case capacity or as titled "Rifle case weight vs volume". In addition to all the fine points Bart B. points out there are other tips and tricks to improve the accuracy of any rifle.
There are endless pages of white papers on how to accurize a rifle, especially GI rifles like the M1 Garand, M 14 and M16 (AR 15 variants). There are also endless books on the subject. Black Magic by John Feamster, The Competitive AR 15 by Glen D. Zediker, Jerry Kuhnhausen also has a few good books on the M1 Garand and M 14 but none of the afore mentioned books is about case capacity or volume nor how to measure it.
Maybe a thread devoted to accurizing tips and tricks for (insert rifle name here) would be in order. Keeping in mind some tips and tricks are match legal while some are not.
Ron
There are endless pages of white papers on how to accurize a rifle, especially GI rifles like the M1 Garand, M 14 and M16 (AR 15 variants). There are also endless books on the subject. Black Magic by John Feamster, The Competitive AR 15 by Glen D. Zediker, Jerry Kuhnhausen also has a few good books on the M1 Garand and M 14 but none of the afore mentioned books is about case capacity or volume nor how to measure it.
Maybe a thread devoted to accurizing tips and tricks for (insert rifle name here) would be in order. Keeping in mind some tips and tricks are match legal while some are not.
Ron
