Do you sort by case weight? Loading To Scale

[Rusty54]

I know this is a topic that has been written about very extensively! But what I have never seen discussed is the actual effect of each grain variation in case weight from the average weight of any specific rifle caliber.

My interest in this wasn't so much to understand the above question but rather to control velocity variations in large volume loading of various mfg & differing weight cases, hence improved accuracy and functioning of semi auto rifle ammo.

So without getting into details I used 5.56nato as well as .243Win for an intermediate volume cartridge and .300 Win Mag for a high volume cartridge as control/ confirming tests.

In the 5.56 round I used 55gr .224 FMJ and fired 10 rounds of each case weight from 88gr to 108gr "though I had to settle for less than 10 rounds of some of the heaviest over 100gr" over my chonograph, while varying the load by -0.1 powder as I increased the case weight by each +1.0gr over 94gr and +0.1gr. powder as I decreased the load under 94gr.Case Weight by each 1.0gr. The reason I chose 94gr as point to vary from is because I found that to be, in my experience as the average 5.56 case weight.

I concider this process, or call this process, Loading To Scale! First you must find a load that is safe and reliable for the average case weight in your caliber and then very your charge "as I stated above" from that. I would then recommend that you take a few rounds of the highest weight cases and lowest weight cases and very the charges to confirm what I have realized for myself. This process also shows why it is important to lower your charge from the highest listed charge in your loading manuals! That if you concider that in the 5.56 extreams I tested there is a 20gr variation in CW, that results in a 2.0gr variation in charge weight using my method.

Just one more thing I should mention is that my brass is as uniform as I can make commercial brass, the necks are turned, flashholes deburred, primer pockets swagged, and cases trimmed to uniform minimum length. If you do not uniform your brass as I do you will likely not be able obtain the results that I do! This process is not for everybody, but only for those who's goal is uniformity of large volumes of mixed types of same caliber cartridges.

 

[338winmag]

I seek to get 3/4 MOA or better at 200 yards for all my hunting rifles. I do not turn any of my caliber necks but otherwise very precise on brass prep and load prep.

I do not cull any brass unless they are not worthy of firing. (Some cull because of weight variances) I do though separate brass according to manufacturer (no ifs about that) The different manufacturer's brass weight and capacity are almost always different and do make a difference.

I also try to use from the same lot my powder, bullets and primers.

 

[Rusty54]

Note in the beginnig thread it may not have been clear that as I decrease CW below 94gr in the 5.56 I increase the charge weight by 0.1gr for each 1.0gr decrease. Sorry for the confusion!

As I stated in my thread, absolute uniformity is a must, and my desire is to develope accuracy as well as reliability in autoloaders, but I found that uniformity in velocity in my 300 Win Mag as well as in the .243 win to be at worst in the teens and more often in the single digits especially in my .300WM and that is with several 10 round groups who's CW varied by 7.0 grain and required a 0.7 gr charge wieght variation.

There certainly is a lot of information I have intentionally left out. Simply because I cannot put it all in the minimal space of this forumn. I actually tried to write it out longhand first and quit when I was almost through the 3rd page because there was too much left to cover that couldn't be put into such a limmited area. As I stated too, this process is not for most people, only those who are interested in large volume loading of one caliber who want the best uniformioty possible, but I believe it is of great interest that of the 3 cartridges I have tested they all seam to vary uniformly by 0.1gr charge weight per1.0gr case weight variation. Or to state it another way, in my testing no matter which of the 3 cartridges I have used, 0.1gr powder equals 1.0gr case weight variation.
This is much more work than the average handloader is willing to do, but I don't believe it is any great leap of understanding, so I don't expect many handloaders to accept this study or process that I have begun using and will use in the future for all rifle ammo I develope. I hope this helps those who are interested!

 

[boomtube]

Not routinely. ??

 

[Bart B]

Sorting cases to a 2% spread in weight's fine for use up through 300 to 400 yards. Beyond that, sort 'em to a 1% weight spread.

The spread in primer output and exact charge weights' powder burning causes a larger spread in pressure and velocity than a 1 or 2 percent difference in case weight. But you need the right combination of powder and primer to make that happen.

For accuracy, milder primers tend to perform better than hot ones. And medium speed powders for the case size tend to do better.

When one loads for highest velocity for a given bullet, they typically end up giving up some accuracy to win the race to the target.

 

[rscott5028]

[...]My interest in this wasn't so much to understand the above question but rather to control velocity variations in large volume loading of various mfg & differing weight cases, hence improved accuracy and functioning of semi auto rifle ammo.
[...]

(1) small variations in case weight don't translate directly to capacity/containment

(2) life's too short to mess with this when dealing with large batches of ammo for semi-auto

(3) if I was able to determine a noteworthy difference between a couple of brands e.g. rws, lapua, RP, then it might be worth tweaking the load by brand

JMHO
-- richard

 

[Lefty7mmstw]

Why bother, trim to length, clean the pocket, load, shoot. 1/2 moa. or less on 6 rifles at present, and 1-1/2 moa. on three with no scopes. Moa. on 2 others.
I've shot three different primers(all standard) and three different brands of brass into the same group with an '06 shooting a 150 grain pill and mid speed powder( twenty years ago so I forget the powder) and the group was sub inch at 100 yards with average extreme spread. I stopped screwing around with brass then and there and focused on getting a bullet the barrel likes and driving it sensibly.
Half of the people on lrh need to take 10% off the top of their powder charges and the rifle will miraculously start shooting great groups. Too many running their rifles ragged and expecting good things.

 

[Lenny Foffa]

YES!!! Always!!! For Hunting loads I try to keep with in 1/2 Grain . Example .270 Win, in Light Win Cases. 185.0 to 185.5 ; Next batch 185.6to to 185.9 . After buying several bags over several years you will end up with several Blue Plastic Boxes of Fired Brass . 25 to 30 rounds in each box, labeled 270 Win Case weights . 185.0 to 185.5 , another 185.6 to 185.9. Another box 186.0 to 186.5 and on and on. I weigh my new brass AFTER I have checked over all length of the each case ; Trim If Necessary ; De Burred and Chamfered the necks, De Burr the INSIDE of the flash hole, and cleaned the Inside of the necks. Then weigh each of them, and put them in the correct box with their brothers. My personal thinking is simply this. Putting the exact same amount of powder(59.5 Grns ) in a case that weighs 184.0 grns and a case that weighs 188.0 grns must result in a different chamber pressure. Both cases have the same outside dimensions after sizing or firing , so the additional weight of the heavier case may mean the walls of the case are thicker, therefore there is less space inside the case. The same powder charge is then confined to a smaller space, and should result in a higher chamber pressure, which will result in a different velocity . All this being said, If your just trying to hit a whitetail from your blind at 100 yards, then what I do is worth nothing, but if your on an expensive hunt and the Trophy Mule Deer is ranged at 500 yards, having uniformed, tested ammo will be a benefit and comfort . IMHO

 

[The Oregonian]

YES!!! Always!!! For Hunting loads I try to keep with in 1/2 Grain . Example .270 Win, in Light Win Cases. 185.0 to 185.5 ; Next batch 185.6to to 185.9 . After buying several bags over several years you will end up with several Blue Plastic Boxes of Fired Brass . 25 to 30 rounds in each box, labeled 270 Win Case weights . 185.0 to 185.5 , another 185.6 to 185.9. Another box 186.0 to 186.5 and on and on. I weigh my new brass AFTER I have checked over all length of the each case ; Trim If Necessary ; De Burred and Chamfered the necks, De Burr the INSIDE of the flash hole, and cleaned the Inside of the necks. Then weigh each of them, and put them in the correct box with their brothers. My personal thinking is simply this. Putting the exact same amount of powder(59.5 Grns ) in a case that weighs 184.0 grns and a case that weighs 188.0 grns must result in a different chamber pressure. Both cases have the same outside dimensions after sizing or firing , so the additional weight of the heavier case may mean the walls of the case are thicker, therefore there is less space inside the case. The same powder charge is then confined to a smaller space, and should result in a higher chamber pressure, which will result in a different velocity . All this being said, If your just trying to hit a whitetail from your blind at 100 yards, then what I do is worth nothing, but if your on an expensive hunt and the Trophy Mule Deer is ranged at 500 yards, having uniformed, tested ammo will be a benefit and comfort . IMHO

How does velocity and accuracy compare across the groups of brass? To me that is all that matters. A difference of about .25% of brass weight may not make a noticeable difference in the velocity or accuracy, or it may. I legitimately don't know.

 

[QuietTexan]

Correlation between case weight and volume does not mean you can determine causation of variance in velocity. You're assuming the weight is uniformly distributed through the walls of the case, and isn't located in the web or case head which make up a larger volumetric percentage of the case weight. Seating depth arguably has a larger impact on case volume than case weight variances, and is easier to measure and improve upon. There is also not a direct relationship between higher case volume and increased velocity because you can't discount the impact of interference fit of the bullet in the neck, bullet jump relative to throating, and several other variables impacting chamber pressure.

There are too many variables to show any causal link between weight, volume, and velocity, which is why when this comes up the people who take the time to gather real data consistently come down to the result of "no causation" even though their data tends to show correlation. There might be correlation, but to show that you have to take both weight and volume measurements on a particular group of cases to make the determination, at which point you've measured the actual capacity so why does weight even matter? Use the better measurement of volume since you have it.

Rifle Brass Sorting Experiment - Part One

Measuring the effects of sorting precision rifle brass cases by weight, capacity, and more.

blog.ammolytics.com

Reloading: Case weight does NOT accurately reflect case...

www.defensivecarry.com

Can case volume be inferred by its weight ? - ozfclass.com

www.ozfclass.com

 

[Mikecr]

Take 2 fire formed cases weighing the same, FL size one of them, reload both, which one provides higher MV?
Answer: The case that was not FL sized.
They both still weigh the same..
Failed test of case weight -vs- load pressure right there.

So no, I do not sort by case weight.

 

[MagnumManiac]

Take 2 fire formed cases weighing the same, FL size one of them, reload both, which one provides higher MV?
Answer: The case that was not FL sized.
They both still weigh the same..
Failed test of case weight -vs- load pressure right there.

So no, I do not sort by case weight.

Me either. I sort my precision brass using a Burette that measures CC's to the tenths.
I can weigh my Lapua brass in 6.5x47 against some RWS I have and the difference is around 3 grains, the volume however is quite different because the RWS has different case dimensions ie thicker case walls and less volume.
Same goes for my Lapua 22-250 brass against my old ww-super 22-250 brass, the Winchester brass has more capacity.
In both instances you would expect the small rifle primer brass to be much heavier, however it is not that big of a difference.
Case web thickness cannot be seen until you measure it or cut a case in half to see the case in profile.
Case weight even from the same manufacture does not always mean the volume is going to be the same.

Cheers,

 

[Coyote Shadow Tracker]

If shooting competition and want each cartridge to have he same POI - Prep your brass exactly the same, load with the same powder charge. Shoot each cartridge, wait 60 seconds between shots and put the velocity on each case. Sort cases by matching the velocity. The cases with very close velocity when loaded again will give you good results.

 

[Bart B]

I tried that but never got those results.

Each case had about the same spread and average velocity.