Question for the experts out there....

Why sort cases by weight when we care about case capacity?

I have done a *whole* bunch of measuring with my 30-06, 308, and 204 ruger brass (Winchester, Remington, Hornaday, Mil-Surp, and Lapua brass where applicable)

I can't find any correlation between case capacity and case weight.

Example -- many of my heavier cases actually hold more water (for the same length) than the lighter ones.

Many cases of the same weight hold *way* more water than other cases of the same weight -- like 308 FGM brass vs Lapua brass -- weighs the same, Lapua holds 0.4g water more per case average.

Has anyone else here tried this out to see what you get?

Thanks

John

First things first.
Sort brass by manufacturer then by lot or year of manufacture.
Then check the weight vs. water capicity of ONE lot of brass. The results are only valid for that specific lot of brass.
This is comparing apples to apples.

Comparing Fed GMM to LC72 to Rem xxx to win yyy will produce only confusion.
This is comparing apples to oranges.

muck

Nope.

I don't mix brass unless I am giving it away to someone who doesn't care, or I am picking up range brass. I don't mix range brass with my "match" brass either.

I weighed cases after case prep and firing.

Only compared cases of like lot and mfg to eachother.

Eg... Box 'O 20 308 FGM once fired in my 308.
Checked for length, weighed, weighed full wet.
No correlation.

50 shells from a Lot 'O lapua 308 fired in my 308.
Case prep, sorted done before firing, etc.
No correlation between weight and water capacity

Same for Aus Mil-surp 308 brass

Same for PS-74 30-06 Mil-surp match prepped (by me) brass.

Same for Win and Rem 30-06 brass.....

Same for 204 Ruger Win, Remington, and Hornaday
brass lots.

What I thought was weird was that
1. Different brands of brass may have vastly different case capacities even though the case weight and "neck wall thickness" is the same.

2. Prep doesn't seem to help the correlation.

3. Through all brands of brass, I couldn't measure a correlation between dry weight and water capacity. AKA, a FGM 308 178.2g (dry) case on average has a different case capacity than a Lapua 178.2g (dry) case -- even when comparing only cases that originally had 0.012" thick necks.

It is my opinion that sorting by weight is a complete waste of time. As you stated in your first post, internal volume is the important factor. Some very good benchrest shooters seperate by weight and yet others dont bother. I guess if it makes you feel better then go for it.

You're loading some relatively large cases. If you were loading small bore varmint and shooting ground hawgs at 300 yds, then maybe it'd matter.

-- Or bench rest comp. I don't know what you're doing.

But for varmints, I always sorted by weight, same lot of brass, same number of previous loadings.

I shave the necks. That affects weight, and won't affect volume.

These days it's 30-06 for deer, 45/70 Govt. for Elk. I don't weigh brass. It's "mixed" --

Shots are generally under 100 yds, and the "effective target" is about a foot diameter.

-- Not saying you're weird, or extreme. Just saying that there are different ways to go. After spending 6 hrs to load 20 rds for .223 Ackley, and putting a Husky torque wrench to the receiver screws, measuring the throat, setting the bullet just off the leade --

I decided I really like shooting surplus Ecuador ammo in an old 8mm Mauser, iron sights, off a sandbag, 700 yards at "stumps" on the hilside.

John, you are doing the right thing. There is not necessarily any correlation between case internal capacity and weight - after all the extra weight could all be in case head or what not...

The problem is, that checking internal capacity is somewhat more involved than checking weight. Presumably you rely on weighing the case empty and full with water?? Any further hints or tips to what methods you use to (efficiently?) measure internal capacity??

- mike

Wow. I always assumed that there was a corelation between case weight and internal volume.
Now I am going to have to wet weight my brass to get case capacity for sorting.
Thanks for sharing this info and for spending the time to "sort out " this problem.

muck

quote:

Originally posted by mho:
The problem is, that checking internal capacity is somewhat more involved than checking weight. Presumably you rely on weighing the case empty and full with water?? Any further hints or tips to what methods you use to (efficiently?) measure internal capacity??

- mike

No real hints -- It is a major pain in the rear ... Definately not "efficient" ..... slow slow slow.

Probably the only thing to speed it up a bunch is a digital scale -- beam scales are way way slow for this sort of thing.

Number all cases with magic marker
Weigh dry
Fill with water
Jiggle and tappity tap cases to ease all of the bubbles up to the top (important step -- bubbles throw off weight alot)
Top off carefully with eye-dropper
Dry off outside with paper towel
Weigh wet
Dump out water
Sit upside down on paper towel
Swab out water
Decap primers
Clean wet primer holes
Sit upside down on paper towel to air dry
remaining water for a couple days

Best regards

John

Knock yourself out!

New saying --

"That's about as much fun as sorting
brass by checking the weight of water held"

TruckJohn,

IMO the "temper" of the brass of each case may have a bearing on your measurement. IE if the brass is maleable and stretches when fired it will hold more......... If the brass is "harder" it will spring back and hold less..... The same (variability) holds true when you resize.

Did you try comparing measurements of the case capacity compared with measurements of case diameter and then relating them to case weight?

In some detailed measurements of the case diameter I have measured as much as .002-.003 difference. Could this have some bearing on your case capacity?

Jim

so.. a 145gr case, when fulled with water is 200gr wet weight say. thats 55gr difference. so that is the same as a 149gr empty with a 204gr wet weight. even thought the cases weight a different ammount they still have the same capacity.


also how tight are you tolerences for weighing them when they are wet. your dry case differences after sorted may be .5gr. but surely a difference of .5gr wet weight is far more significant in the scheme of things

that comparison is only good if you are burnin water?
What happen when you use powders ?
And to make it more complicated, diffrent powders with diffrent burn rates and u get it dont you.
follow this link, http://www.castbullet.com/reload/vmd.htm and read. it is the only way i know that you can measure volume correctly.
the only reason to weigh brass is to get all you cases as consistent as possible.

quote:

Originally posted by pdhntr1:
TruckJohn,

Did you try comparing measurements of the case capacity compared with measurements of case diameter and then relating them to case weight?

In some detailed measurements of the case diameter I have measured as much as .002-.003 difference. Could this have some bearing on your case capacity?

Jim

I suppose it could have some effect on the case capacity measurements. You may be on to something.

Please measure some and check actual water weights, then post your results back here. 50 cases should give enough data for a linear regression analysis.

Just make sure the brass is from the same lot, same # of firings, etc.

Without data, it is just opinion or Witch-craft.

Thanks

John

As mentioned elsewhere in AR this morning, the British National Team found weighing the complete loaded rounds and sorting into batches by weight did provide them with better scores at longish ranges (800,900, and 1,000 yards), when firing 7.52 Nato/.308 ammunition.

I do not pretend to know why that worked, nor did they, but it demonstrably worked for them when they were shooting as a team in various iternational competitions....and winning regfularly against all comers.

quote:

Originally posted by TruckJohn:

quote:

Originally posted by pdhntr1:
TruckJohn,

Did you try comparing measurements of the case capacity compared with measurements of case diameter and then relating them to case weight?

In some detailed measurements of the case diameter I have measured as much as .002-.003 difference. Could this have some bearing on your case capacity?

Jim

I suppose it could have some effect on the case capacity measurements. You may be on to something.

Please measure some and check actual water weights, then post your results back here. 50 cases should give enough data for a linear regression analysis.

Just make sure the brass is from the same lot, same # of firings, etc.

Without data, it is just opinion or Witch-craft.

Thanks

John

I suppose it could have some effect on the case capacity measurements. You may be on to something.

And logically what would be the next step on your part?


Please measure some and check actual water weights, then post your results back here. 50 cases should give enough data for a linear regression analysis.

Just make sure the brass is from the same lot, same # of firings, etc.

I am on your side, but the ball is in your court. Prove me wrong. I can handle it.

Without data, it is just opinion or Witch-craft.

quote:

Originally posted by pdhntr1:

In some detailed measurements of the case diameter I have measured as much as .002-.003 difference. Could this have some bearing on your case capacity?

The data that is required to support my opinion is provided. I posted my data to try to help you figure out a problem you may have. I won't make the same mistake again.

Jim

To measure case capacity, I like to use a ball powder like H414. It's too easy to get a bubble or two that will throw your results off. I only use it to decide how much to change the charge when changing from Win. to Rem. cases for example. They also all have to be freshly trimmed to the same length or you're definitely wasting your time. If you use powder you don't have a bunch of wet cases either.