case weight

[chet]

i have been loading some lapua and LC brass for my 223 weighting around 94grs, i have a few once fired PMC brass that weighs 104grs, i dropped my charge 1/2 gr on the powder, any thoughts.

chet

 

[cw308]

Chet
You did the right thing . Years back I shot only Rem. & Win. brass , when a shooting friend shooting the same caliber and has no interest in reloading gives me all his brass . Federal , HSM and ADI brass . With the R&W brass my powder charge would fill the case to the base of the neck , when using his brass the powder would fill the case to the top of the neck . I never thought different brass could be much thicker and of course less volume. I'm using IMR 4064 in a 308 case , it's a stick powder not the easiest to meter but works well for me with the thicker brass and lower charge , .5 grains lower then listed charges , I prefer the thicker brass . You did the right thing in lowering your charge. Always best to be safe .

Chris

 

[Uncle Ed]

i have been loading some lapua and LC brass for my 223 weighting around 94grs, i have a few once fired PMC brass that weighs 104grs, i dropped my charge 1/2 gr on the powder, any thoughts.

chet

The difference in case capacity between the top Lake City case at 30.6 and the bottom old Lapua at 28.0 with a 55 grain bullet and 25.0 grains of H335 is a increase of 6,000 psi due to the lower capacity. The charge of 25.0 grains of H335 puts the old Lapua case at 28.0 at approximately 55,000 psi and the Lake City case at 49,000 psi according to Quickload.

 

[rammac]

Case capacity and case weight are not directly related, I have at least one study available that proves it. Brass used to make cartridges can vary in density due to it's content. Cartridge brass is not all brass nor do all brands use the same kind of brass alloy. Cartridge brass is made up of some brass alloy mixed with zinc, iron, silicon, and some brands even add chromium. The various combinations of that content will change the density and weight of cases even if the cases have the same volume.

Yes, if you are a bench rest competitor then I can understand you wanting to match cases as closely as possible but even then the case volume should be checked rather than just weighing the cases.

Using distilled water is the best way to verify case volume, not by pouring powder in to the case. Powder will not fill the cases properly because there are air spaces around the powder granules, it wont reflect the true case volume. When you are evaluating case volume you are doing it to estimate the effect on the hot gasses that the burning powder produces and water simulates how those gasses will fill the case better than anything else that is available to the average reloader.

 

[seymour fish]

Case capacity and case weight are not directly related, I have at least one study available that proves it. Brass used to make cartridges can vary in density due to it's content. Cartridge brass is not all brass nor do all brands use the same kind of brass alloy. Cartridge brass is made up of some brass alloy mixed with zinc, iron, silicon, and some brands even add chromium. The various combinations of that content will change the density and weight of cases even if the cases have the same volume.

Yes, if you are a bench rest competitor then I can understand you wanting to match cases as closely as possible but even then the case volume should be checked rather than just weighing the cases.

Using distilled water is the best way to verify case volume, not by pouring powder in to the case. Powder will not fill the cases properly because there are air spaces around the powder granules, it wont reflect the true case volume. When you are evaluating case volume you are doing it to estimate the effect on the hot gasses that the burning powder produces and water simulates how those gasses will fill the case better than anything else that is available to the average reloader.

Brass is a combination of copper and zinc, thus your statement “some brass alloy Mixed with Zinc” is both redundant and sloppy. Your initial assertion is correct and does not require citing any “study” to prove it. One can easily satisfy himself of that in a few minutes. Your notion of what you are doing when evaluating case volume and “the effect on hot gasses” is difficult to grasp. Can you expand on this ?

 

[mikecr]

rammac is right in that case weight and capacity are not directly correlating.
As far as composition, it may very well be that harder cartridge brass(like some Lapua) springs back to different case capacity than softer brass(like some Norma).

 

[Dusty Stevens]

Its easy to say cases made years apart may vary in weight due to brass composition but out of the same box will be made from the same sheet of brass and therefore if the brass is the same on the outside and weights vary its pretty safe to say the difference is 99%+ volume related. In not talking an LC68 compared to a remington case from 2008 im talking quality brass from the same lot. Just different extractor groove measurements can be seen from lot to lot so that accounts for big weight differences

 

[Ned Ludd]

Variance in case volume due to variance in brass composition should never be the biggest of someone's worries, it's far too small a source of error. Sorting cases by weight is obviously easier than determining actual water volume when working with large numbers of cases. However, variance in the extractor groove dimensions, as well as external case dimensions, such as base to shoulder, can change the internal volume without altering the weight. For that reason, if you prepare a graph of case weight versus case volume, you will typically observe a trend line that has a negative slope. In other words, as case weight increases, case volume generally decreases. However, you will almost always find a few outliers that lie far off the trend line for the reasons mentioned above. So sorting brass by weight is not a perfect substitute for determining actual water volume. Nonetheless, cases sorted only by weight will generally exhibit more consistent internal volume than cases that have not been sorted at all.

 

[XTR]

Case capacity and case weight are not directly related, I have at least one study available that proves it.

There is at least one post on this site that reported different results.

I used to have a bookmark to the post but when the site was redesigned a couple of yrs ago it broke the link and I can't tell where it is now. From what I recall that test showed was a 70% correlation between variation in case capacity and brass weight for 223 brass. Now I believe that was done with LC brass and not various brands.

 

[Twicepop]

You changed a major component, IMHO you should do more than just drop a half grain, start at the bottom and work up again.

 

[Ned Ludd]

There is at least one post on this site that reported different results.

I used to have a bookmark to the post but when the site was redesigned a couple of yrs ago it broke the link and I can't tell where it is now. From what I recall that test showed was a 70% correlation between variation in case capacity and brass weight for 223 brass. Now I believe that was done with LC brass and not various brands.

There is definitely a correlation between case weight and case volume. If @rammac or others believe that there is not, I would suggest they determine it for themselves using a statistically significant number of cases. They will find that there most certainly IS a very good correlation. I have measured case weight and water volume for more cases than I care to think about. As case weight increases, case volume decreases, consistently giving a trend line with a negative slope on a graph of case weight versus case volume. In my hands, correlation coefficients for the trend lines with Lapua .223 Rem brass has ranged from around 0.6 to over 0.9, depending on the specific Lot# of brass and how many cases were tested at a time. There are always at least a one or two outliers, sometimes more - again, depending on how many cases were tested.

My earlier point was that sorting cases by weight will not remove or segregate those outliers. I do believe that sorting by weight improves internal volume consistency as compared to doing nothing at all, and I use the weight-based approach to sort brass regularly. However, determining actual case volume is certainly the more accurate method, but it is relatively slow and painful when large numbers of cases are involved.

 

[LA50SHOOTER]

Measuring water or any liquid (distilled or tap) isn't an exact science either even if all cases are trimmed to the same length IMO. - I've seen some pretty big swings in the weight of water dispensed especially in larger cases and that is filling them right up to the overflow point.

I sort by weight of case after I've uniformed primer pockets & flash-holes & neck-turned (FWIW). - Then put them in an ammo carrier box from light to heavy (or multiple boxes if I'm working with a larger lot of brass) corresponding by numbers & put a tally sheet in the lid that shows case weight by row number. - Another thing I do is watch the velocities produced during firing & record them by file number on the SD card in Lab Radar's memory. - If I see one that "sticks out" then I note it during the test firing and evaluate if I'm going to pull it or reposition it in the line-up. - I've seen velocity trend with case weight and that is weighing powder charges to 0.02 of a grain & bullets sorted by bearing surface length & weight. - For good quality brass I feel that it's about an 80 to 85% accurate proposition based on velocities recorded.
- My conclusion is that weighing fully processed brass by weight is about as good as I'll be able to get it. - For sure not 100 % accurate but I believe it is better than no sorting method at all. - And I'm speaking about using brass that is manufactured by Lapua, RUAG/RWS, Peterson, Norma & Nosler that is shot out of a accuracy type bolt gun. - Brass for a AR type platform I'm not sorting (Hornady, Winchester, Etc.) but I'm not mixing brands or lot numbers on it either.

 

[mikecr]

I sort by fully fire formed H20 capacities, and really couldn't care less about case weight.
I'm sure in some situations, sorting by case weight is NOT better than nothing, but worse.
And the only way to know is to just measure capacity. So that is why I do it.

It's a similar situation with culling bullets by base to ogive, instead of considering all that makes up this range.
While you don't understand the actual deviation, you don't know if it's good or bad overall.

 

[KevinThomas]

I’m not quite sure where all the conjecture relating to alloy and weight variation comes in, but as a rule, virtually everyone in the industry uses 70/30 cartridge brass for case production. Any other metals involved are little more than impurities, essentially trace elements within that 70/30 alloy. That’s not to say that the brass used by various manufacturers is the same, it most assuredly isn’t. Purity of the alloy, whether its virgin material or recycled blends, the production process that gives the material grain size and structure, all this comes into play as to how well the material will form, and just how good the end product will be. But I’d be shocked to see weight variations of any note being caused by differences in the alloy itself.

While many focus on case weight, it really isn’t a good indicator of capacity at all. Variation in case capacity is controlled primarily by the punches used in drawing the cases. As they come off the presses, the partially formed cases should have virtually identical capacities, assuming there’s nothing changed during that portion of the run. Weight variations in finished cases are the result of other operations that are performed on the case exterior, such as the heading operations that creates the primer pocket, flash hole and cuts the extractor groove. None of these have any bearing on the internal capacity, but very slight variations in how these operations are performed can greatly effect the weight of the finished case.

So why is case weight variation such a hot topic? Because on the face of it, it makes sense that it should be indicative of some difference, and internal capacity would seem to be a likely candidate for being that variable. Ani’s their very simple reason is that case weight variation is very easy to check, while actual water capacity is a real pain in the ass. As a result, many folks will take the fast and easy approach, downplaying the fact that it’s not giving you good data.

My advice here is, take note of the case weight when comparing different brands or runs of cases, and take really significant differences as a good reason to check the actual capacity via water. Aside from that,if you’re dealing with quality brass to begin with, that variation probably isn’t going to be a real concern in the finished product.

 

[LA50SHOOTER]

I'd like to hear from the 1000 yard Benchrest guys who have shot some good groups about how & if they address this subject. And explain any logic for the method they may use.


mikecr Sir, - You've stated in your post,
I sort by fully fire formed H20 capacities, and really couldn't care less about case weight. - How exactly are you controlling the water level to "over-flow" point - and are you trimming all your cases to the same length ? - I've tried this method of filling cases to the "over-flow" point and weighed the water. - Then repeated it over again (several times) with the exact same piece of brass and I definitely found variations in this process which indicates to me that its not precise enough to where I feel it establishes a valid capacity.
I'm sure in some situations, sorting by case weight is NOT better than nothing, but worse. - How could it be worse ? - A bunch of cases from the same lot are just that, nothing more, nothing less - If one chooses to just use them and forgo the "case capacity" step, the cases are going to get shot one way or another sooner or later and the only way to know how good they do is to try them.
While you don't understand the actual deviation, you don't know if it's good or bad overall. - You've totally lost me on this statement.
- And if it's directed at myself or someone else, whom ever the "you" is, then I can only say that this is an ambiguous statement. (because whom ever "you" is, is not known by yourself in regards to really anything at all)

- I'm not here to rock-the-boat, but I know what results I've achieved after using sort-by-weight as a method. (The Target down range and the Lab Radar chronograph are what I'm using as a "standard" for results)- I have to put trust somewhere in the process that I've chosen and the chronograph and the target are the 2 items that I've picked to determine the validity of the method that I sort by.

- Ron -

 

[Dusty Stevens]

I'd like to hear from the 1000 yard Benchrest guys who have shot some good groups about how & if they address this subject. And explain any logic for the method they may use.


mikecr Sir, - You've stated in your post,
I sort by fully fire formed H20 capacities, and really couldn't care less about case weight. - How exactly are you controlling the water level to "over-flow" point - and are you trimming all your cases to the same length ? - I've tried this method of filling cases to the "over-flow" point and weighed the water. - Then repeated it over again (several times) with the exact same piece of brass and I definitely found variations in this process which indicates to me that its not precise enough to where I feel it establishes a valid capacity.
I'm sure in some situations, sorting by case weight is NOT better than nothing, but worse. - How could it be worse ? - A bunch of cases from the same lot are just that, nothing more, nothing less - If one chooses to just use them and forgo the "case capacity" step, the cases are going to get shot one way or another sooner or later and the only way to know how good they do is to try them.
While you don't understand the actual deviation, you don't know if it's good or bad overall. - You've totally lost me on this statement.
- And if it's directed at myself or someone else, whom ever the "you" is, then I can only say that this is an ambiguous statement. (because whom ever "you" is, is not known by yourself in regards to really anything at all)

- I'm not here to rock-the-boat, but I know what results I've achieved after using sort-by-weight as a method. (The Target down range and the Lab Radar chronograph are what I'm using as a "standard" for results)- I have to put trust somewhere in the process that I've chosen and the chronograph and the target are the 2 items that I've picked to determine the validity of the method that I sort by.

- Ron -

Very spot on ron.
Lots of vendors that cater to the ppc crowd sell cases sorted by weight. Ive never seen any selling them sorted by h2o capacity. People just take for granted that the heading process held a good tolerance during a single lot run and the extractor groove cutting tool didnt break or get replaced. So therefore most go with the fact that if theyre the same on the outside and they dont weigh the same the capacity is going to be different whether its a thicker base or thicker wall.

 

[LA50SHOOTER]

Very spot on ron.
Lots of vendors that cater to the ppc crowd sell cases sorted by weight. Ive never seen any selling them sorted by h2o capacity. People just take for granted that the heading process held a good tolerance during a single lot run and the extractor groove cutting tool didnt break or get replaced. So therefore most go with the fact that if theyre the same on the outside and they dont weigh the same the capacity is going to be different whether its a thicker base or thicker wall.

- Thank You,
And I'm here to learn / acquire knowledge. - If someone can present a method that is based on test/trials that makes good sense for the arduous task of determining case capacity and it has worked for them, then I'm very willing to listen and try it. - Again, using the chronograph and the down-range target as the "standard" by which results are determined.
- I have measured cases from the meager 223 Remington all the way up to 50 BMG Improved including a whole bunch of calibers in between. All the while doing so, thinking to myself, should I be doing this in a "raw" weight state or is fully prepared brass the better way to go ??
- And I'm doing it with what we as accuracy minded shooters consider to be high quality brass. - Some of the larger calibers I've noted some pretty big weight differences in an entire lot of 500 pieces of brass (CheyTac based cartridges especially using Bertram brass, before Peterson had come to market with its offerings) - When I say "big weight differences", I'm talking about 10+ grains difference from lightest to heaviest. - My thoughts are that I shouldn't group the lighter in weight pieces of brass with the heavier ones, but I have not run a test to conclude if in fact the weight difference from lightest to heaviest, if mixed in the same 5 shot group makes a difference at the target & recording with the chronograph. (Maybe something to consider & try just to see what the out-come is and if there's true validity to the method that I'm currently using).

- Ron -

 

[Texas10]

When sorting 223 cases by water volume I found that it is absolutely essential that all cases are fully fire formed in the same chamber and sorted by base to shoulder dimensions, then trimmed. Even then, getting the water filled to the top but not slightly over is a challenge. Lacquer thinner works better due to its lower viscosity, but a bit of a pain to dispense, not to mention the odor and flammability factors.

Sorting new cases or range pick up is a total waste of time for the reason pointed out above.

One factor that I can see will cause variances in case volume during production is lubrication used, what and how much will change the hydraulic volume added to the dies displacement. This presumes a lubricant is used for the drawing operations, I don't know for sure in brass case production, just know from experience working with steel and it's alloys.

I don't shoot in competition, so weighing brass is the best method to sort. In my experience it's the best use of my valuable time.

 

[mikecr]

Ron,
'how to accurately measure H20 capacity' should be another thread, or thread search: http://forum.accurateshooter.com/se...o+accurately+measure+H20+capacity&o=relevance
How could sorting by weight be worse than not sorting at all? Because of the sorting part, which is acting on weak basis. If you need to separate and use best capacity match of 50 cases, you don't really get there, that you know of, using shortcuts and assumptions. You get there through planning, preps, direct measurements, and understanding.
So you might cull 5 cases deviating in weight, while leaving 3 cases in the remaining 45 that still deviate in capacity. You lost 2 extra cases gaining nothing over doing nothing.
On the other hand, if you simply cull the 3 deviating by capacity, you'd be down to 47 cases -while meeting your objective.
While you don't understand the actual deviation was not towards you personally. This could be WE, or I. And the context of this is that there is no real gain without understanding.
If we ask someone what to do and follow a direction given, regardless of apparent result, we gain nothing real until understanding it. If we try something and it seems to work, it hasn't really until we understand what is working. That is, we've isolated/tested something in particular to understand, and drawn a conclusion on this valid attribute.

Otherwise we're left with generalizations, rules of thumb, loose notions, common fallacies, and hearsay. Much, of little actual value.

 

[LA50SHOOTER]

Ron,
'how to accurately measure H20 capacity' should be another thread, or thread search: http://forum.accurateshooter.com/se...o+accurately+measure+H20+capacity&o=relevance
How could sorting by weight be worse than not sorting at all? Because of the sorting part, which is acting on weak basis. If you need to separate and use best capacity match of 50 cases, you don't really get there, that you know of, using shortcuts and assumptions. You get there through planning, preps, direct measurements, and understanding.
So you might cull 5 cases deviating in weight, while leaving 3 cases in the remaining 45 that still deviate in capacity. You lost 2 extra cases gaining nothing over doing nothing.
On the other hand, if you simply cull the 3 deviating by capacity, you'd be down to 47 cases -while meeting your objective.
While you don't understand the actual deviation was not towards you personally. This could be WE, or I. And the context of this is that there is no real gain without understanding.
If we ask someone what to do and follow a direction given, regardless of apparent result, we gain nothing real until understanding it. If we try something and it seems to work, it hasn't really until we understand what is working. That is, we've isolated/tested something in particular to understand, and drawn a conclusion on this valid attribute.

Otherwise we're left with generalizations, rules of thumb, loose notions, common fallacies, and hearsay. Much, of little actual value.

So what your telling me is my method of weighing is "of little value" ?? - Not to be obstinate, but the results I've yielded tell me otherwise.
Perfect - No, as good as possibly your method, maybe not, but I claimed 80-85% accurate proposition based on velocities recorded, many of which have exhibited single digit ES. To me this is an improvement and it "justifies" the time spent to perform the step of sorting all pieces of brass in a lot by weight. - I'm not using shortcuts or assumptions and Every piece of brass gets tested, I don't throw away the ones that are light or heavy, I'm simply grouping by weight, then loading and testing. - In my mind it far exceeds just dumping them in a MTM box, especially when we are talking about lots of brass that usually have 200 pieces of brass or more and in some cases 500 or more. - The largest lot I've worked with was 1,600 pieces of Norma 300 WSM brass. - I can't begin to fathom checking that with water or any other fluid, I simply don't have the additional time.