Sorting Cases by Water Capacity

I think it was the discussions in Doc's brass thread that got me thinking about sorting cases by water capacity in grains. I'm in the middle of a project where I was about to sort by head stamp and case weight, like I've always done when reloading for more than just range fun. Reading several opinions in Doc's thread (advocating that sorting by water capacity weight is more accurate) started me wondering if I've been wasting my time all these years. Many outdoor writers these days will point out that case capacity (measured in grains of water) is more accurate than sorting the way I do. I don't know if these water capacity tests are widespread or if people are simply opining with, well ... opinions. Personally, I've never tried this before.

So anyway, I'm working quite a bit with .338 Lapua Magnum at the moment, so figured focusing on that cartridge wouldn't take me too far away from what I'm already doing. Of the brass I've used for reloading .338, PPU seems to be the least consistent by any measure; considering weight, neck thickness/uniformity, and firing stretch deltas, everything about this brass is more erratic than the other brass I've loaded in .338. Admittedly, the brands I use cost more, much more. If fact, the only reason I have PPU brass is that I picked up some of Syd’s Ammo hand loads at a show earlier this year and he used PPU. So that's what I plan on using here.

I guess the most meaningful measure is accuracy and consistency of bullets at the muzzle and at applicable distances downrange. But for what I'm planning to do here today, I'm limiting the scope to "sorting brass by weight versus sorting by water capacity weight" to determine whether the two different methods of sorting would result in different groups (of 5), for 5-round load development and/or accuracy tests: If I sort 10 cases by weight and separated them into two 5-round groups, then sort the same 10 cases by water capacity weight, will I end up with two different 5-round groups? If the answer is "no", then I might not explore this topic any further. If yes (or if I notice any anomalies in the data I collect), then maybe another science project out on the range is in order.

I'll come back on and post again when I get some results.

Dare I ask: "What are you trying to fix?"

GUNSnROTORS said:

I think it was the discussions in Doc's brass thread that got me thinking about sorting cases by water capacity in grains. I'm in the middle of a project where I was about to sort by head stamp and case weight, like I've always done when reloading for more than just range fun. Reading several opinions in Doc's thread (advocating that sorting by water capacity weight is more accurate) started me wondering if I've been wasting my time all these years. Many outdoor writers these days will point out that case capacity (measured in grains of water) is more accurate than sorting the way I do. I don't know if these water capacity tests are widespread or if people are simply opining with, well ... opinions. Personally, I've never tried this before.

Click to expand...

Weighing cases? After wasting a lot of time and discarding a LOT of brass (I once set aside 80 cases from a 200 case lot that cost me about a dollar a case...), I have found that I have been wasting my time. Further, long time friend Vern Harrison, who had set several 1k benchrest records, strongly steered me away from this useless technique.

When you weigh brass, you are seeing variations in rim thickness, for an easy example, that don't contribute to capacity changes. Even if we identify weight variations that seem to matter, we must remind ourselves that a certain weight variation in brass is a very long way from being a corresponding variation in volume/powder capacity.

So anyway, I'm working quite a bit with .338 Lapua Magnum at the moment, so figured focusing on that cartridge wouldn't take me too far away from what I'm already doing. Of the brass I've used for reloading .338, PPU seems to be the least consistent by any measure; considering weight, neck thickness/uniformity, and firing stretch deltas, everything about this brass is more erratic than the other brass I've loaded in .338. Admittedly, the brands I use cost more, much more. If fact, the only reason I have PPU brass is that I picked up some of Syd’s Ammo hand loads at a show earlier this year and he used PPU. So that's what I plan on using here.

I guess the most meaningful measure is accuracy and consistency of bullets at the muzzle and at applicable distances downrange. But for what I'm planning to do here today, I'm limiting the scope to "sorting brass by weight versus sorting by water capacity weight" to determine whether the two different methods of sorting would result in different groups (of 5), for 5-round load development and/or accuracy tests: If I sort 10 cases by weight and separated them into two 5-round groups, then sort the same 10 cases by water capacity weight, will I end up with two different 5-round groups? If the answer is "no", then I might not explore this topic any further. If yes (or if I notice any anomalies in the data I collect), then maybe another science project out on the range is in order.

I'll come back on and post again when I get some results.

Click to expand...

The .338 Lapua is very sensitive to velocity variation because we tend to use it out where velocity really matters. When we have large variations in muzzle velocity, we will immediately see this telegraph to the most distant targets in the form of vertical stringing. Even with good brass, the successful long range handloader will be challenged to find a good load with minimum standard deviation, because the .338 uses a large amount of powder in a large vessel. We were able to get standard deviation down to about 7-8 fps with several rifles using unsorted Lapua brass.

More fooling around may have provided slightly better results, but when you can blow the wind call by 1 mph and the bullet lands further from center than your velocity deviations take you, as some point you are barking up the wrong tree...

With brass like PPU, not only do we suffer capacity variations, but we also have case wall runout and neck tension variations that will contribute to inconsistent results.

Maybe (MAYBE!), once you trim them, chamfer them, turn the necks, cut the primer pockets and true up the heads, you could sort PPU by capacity and see meaningful results. Otherwise, IMHO, you are just polishing a turd. If you want to use them, I would suggest using them to load ammo for your less critical applications, like position shooting or loading mid-range hunting ammo.

Rather than dwelling on brass variations and other tedium, I have found much better success and quicker results using Dan Newberry's OCW system for finding a good load. The loads located by using this system will be more tolerant of small variations that one will always find in brass, bullets and primers.

Measurements:

Started with 10 sized, trimmed, clean PPU cases and weighed them.

Then added a square of gorilla tape to each base and weighed each case again. I had already de-capped them, so I decided to do it this way rather than prime them and then add water...setting off a chain reaction of wet primer tests ...

Then filled each case with tap water and weighed them again. Scale I used is only accurate to 0.1 grains, so didn't bother with measuring temp, ph, or tds. Only half kidding there, I figure if anybody actually reads this thread, there's a 3% chance someone will gig me on it.

(I ruled out filling cases with water and dumping into a measuring pan because I knew I wouldn't be able to extract all of the water. We all know it takes a great deal of time to dry cases and I didn't want to add a variable if there was an easy way to eliminate it.)

Took notes by hand and will put data in an excel table next.

This was the setup:

Results:

In the first table, brass is sorted by brass weight and numbered 01-10:
Rounds 01-05 would be used for the first group.
Rounds 06-10 would be used for the second group.

In the second table, brass is sorted by water capacity:
Though the order (by brass #) has changed showing variability in the correlation between brass weight and water capacity, the rounds included within each of the two 5-round groups remain the same.

This test was very limited in scope: only ten cases from only one manufacturer. Further, the scale used is not very precise, etc., etc. A drop of water from the injector I used weighs 0.58 grains (10 drops = 5.8, then I divided by 10). Even though I took great care to be consistent, I could have been off by a drop. No doubt a larger sample might lead to anomalies revealing more subtle trends, however, this trend (correlation of weight vs. capacity) makes sense and should generally apply. I should have predicted it. In fact, I'm more than a bit embarrassed that I didn't. If any of you guys are doing some form of case weight/water capacity weight delta sorting operation, well, more power to you. Considering that the water sorting process takes much longer and yields similar (if not identical) results, I'm sticking with simply sorting by head stamp, lot# (when available), and case weight.

The results are pretty much what I "should have" expected - with metallurgy and outside case dimensions being equal, a lighter case should have greater capacity, and will correspondingly hold more water. Likewise, heavier cases with identical outside dimensions will have less inside capacity and hold less water.

E.Shell said:

...Rather than dwelling on brass variations and other tedium, I have found much better success and quicker results using Dan Newberry's OCW system for finding a good load. The loads located by using this system will be more tolerant of small variations that one will always find in brass, bullets and primers.

Click to expand...

Thanks very much Ed for your detailed reply. I "know" you are a subject matter expert and I respect your knowledge very much. I did this as much in reply to other threads as for my own edification. Admittedly, I do sort cases by head stamp/case weight, not always. I'm the product of numerous gun writers who advocate the practice. I think my meager test results in this thread prove your statements above, so maybe I can break myself from a bad habit.

I will also take your advice and read up on Dan Newberry's OCW system.

E.Shell said:

Dare I ask: "What are you trying to fix?"

Weighing cases? After wasting a lot of time and discarding a LOT of brass (I once set aside 80 cases from a 200 case lot that cost me about a dollar a case...), I have found that I have been wasting my time. Further, long time friend Vern Harrison, who had set several 1k benchrest records, strongly steered me away from this useless technique.

When you weigh brass, you are seeing variations in rim thickness, for an easy example, that don't contribute to capacity changes. Even if we identify weight variations that seem to matter, we must remind ourselves that a certain weight variation in brass is a very long way from being a corresponding variation in volume/powder capacity.The .338 Lapua is very sensitive to velocity variation because we tend to use it out where velocity really matters. When we have large variations in muzzle velocity, we will immediately see this telegraph to the most distant targets in the form of vertical stringing. Even with good brass, the successful long range handloader will be challenged to find a good load with minimum standard deviation, because the .338 uses a large amount of powder in a large vessel. We were able to get standard deviation down to about 7-8 fps with several rifles using unsorted Lapua brass.

More fooling around may have provided slightly better results, but when you can blow the wind call by 1 mph and the bullet lands further from center than your velocity deviations take you, as some point you are barking up the wrong tree...

With brass like PPU, not only do we suffer capacity variations, but we also have case wall runout and neck tension variations that will contribute to inconsistent results.

Maybe (MAYBE!), once you trim them, chamfer them, turn the necks, cut the primer pockets and true up the heads, you could sort PPU by capacity and see meaningful results. Otherwise, IMHO, you are just polishing a turd. If you want to use them, I would suggest using them to load ammo for your less critical applications, like position shooting or loading mid-range hunting ammo.

Rather than dwelling on brass variations and other tedium, I have found much better success and quicker results using Dan Newberry's OCW system for finding a good load. The loads located by using this system will be more tolerant of small variations that one will always find in brass, bullets and primers.

Click to expand...

The professor has spoken...
Dan!s OCW is a good start, there are spreadsheets out there that will help, if you are so inclined.
Lapua brass, Berger's or Lapua bullets, with IMR-7828, TRG-42, S&B glass.

-Rock