Weight sorted cases ..

I have done this myself on a few occasions and no doubt many others have as well. The question is, just how much actually dimensional physical difference there is between cases of different weights. Some folks swear by weight sorting cases, on the opposite end of things others couldn't care less. The other night on a whim, couldn't sleep. I weighed the anvil from a small pistol primer, 0.5grs according to my Hornady digital scale. I did some number crunching, keep in mind I not am a math whiz, and my methodology on this informal test so speak has a few flaws. If someone wants to measure, weigh, and crunch in order to come with an exact figure, be my guest. The whole point is just "have fun" and get a very informal guestimate on just how much physical difference 0.5grs in case weight might make in actual volume. We all know case weight can and does vary from lot to lot, make to make, and commercial vs. military, that is not intended to be part of the discussion.

I took a fired 38 Spcl case (that was what was siiting on my bench at the time, pretty close to a cylinder and easy to calculate volumes), measured the inside length from the top of the web to the case mouth and the inside diameter of the case mouth.
Inside length: 0.993", inside dia. 0.359", this gives the a volume of the 0.10046 cubic inches.

Next I weighed the case, it came out a 80.9 grs. If we had a case or a batch of cases that weighed 0.5grs heavier at 81.4grs that would an increase in weight of 0.00618%, and would in turn decrease the internal volume to 0.09137 cubic inches, or by 0.00909 cubic inches. this based upon an even distribution of brass in the case. In actual practice it could be in one or more of the following where applicable, case neck, shoulder, body, web, and/or head.

A few take aways:
1. 0.5gr or 1.0grs evenly distributed in a case does not make much difference in actual volume.
2. If/when differences in case weight do make a difference, it does not take much.

Michael

I cannot argue with your logic. Perhaps the difference doesn’t lay with the amount of the excess brass (or thinner brass) but more in the distribution of the error. For example, if the web is thicker or maybe the shoulder wasn’t drawn properly? Pure speculation on my part.

I can say that I weigh rifle cases when I’m working for the very best ammo but I can’t say that makes the difference between consistent cartridges and maybe less consistent cartridges. If it was the only step I took, it might have more significance but it’s one of many steps.

A friend had a 700 BDL that quit shooting his preferred load . I had a hunch after my own journey so I weighed 120 factory 06' 1x cases from one lot according to the box flap . I'd say 192-205 gr is a big split 13 gr of brass is pretty close to 4 buck or TTT in lead shot .

RBHarter said:

A friend had a 700 BDL that quit shooting his preferred load . I had a hunch after my own journey so I weighed 120 factory 06' 1x cases from one lot according to the box flap . I'd say 192-205 gr is a big split 13 gr of brass is pretty close to 4 buck or TTT in lead shot .

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Agreed but that is a significant difference. (13 gr) and maybe that's the key. If the difference in weight is large, then the difference in volume may be enough to matter.
So perhaps a 1/2gr in an 80 gr case isn't a big deal but 13 gr in a 192 gr case is??
I don't know but I think it's a topic worth looking into.

Edit. fixed the grain - gram error

The Prima Donna Savage demanded 1 gr or less to deliver groups .
His 700 would deliver on 5 gr .
Had a 308 that would deliver 2" within 4" with whatever fell off the shelf with the same loads .

I have a heavy barrel 700 chambered in 308 that will make one hole groups all day, if you feed it the right load. I had a another 700 that wasn't as picky; It would shoot 4" to 1" groups, regardless of what you fed it in the same bullet weight.
There was no sense in weighing cases for the latter but I had to be a lot more careful with the former.

Weighing cases is not something I've ever done. I weighed the 60 cases I use for local matches this week and posted the results in another thread. 43 were +/- 0.5gr. 16 were +/- 1 gr and 1 was 1.2 gr. I thought that was pretty good, but have zero feel for what is truly good. Quite a few were zero, so might take 5 each of zero weight variance and shoot them for group. Will weigh the bullets for zero variance as well. Will be interesting. Local 100 yd range is narrow with berms and trees down both sides, so reduced or minimal cross winds.

I usually go plus or minus .1gr seems to do real well for me.

Never weighed cases, but I have bullets. I think this is one of those, "It doesn't matter...until it does." issues.

I had quite a few that were identical. 0.0gr difference. They are Federals.

I weigh cases to reduce inconsistencies for my testloads. As for .38 Special cases, I separate by headstamp because there is a noticeable difference in weight between brands. I never measured case dimensions, but the additional weight is in the walls and head. IMI brass for example has the thickest walls among other brass casings. That means that if you swage the Outside diameters to the same dimension, the inside dimensions will vary. This isn't good for cast bullets because now your bullet diameter can vary from the slight swaging caused by seating lead bullets in them. This is great if you want to shoot plastic bullets cast from a bullet mold. A Lee 38-160 FRN cast plastic bullet will fall through a resized Rem case but will fit snug and hold its place in an IMI case.

I am reasonably sure that smokeless powder "A" will not act the same as smokeless powder "B", when given a case capacity variance of 0.00909 cubic inches.

For that simple fact, I will say the same thing as Bret did, "It doesn't matter...until it does."

The few times I did weigh cases I did so after trimming to same length, reaming primer pockets, and deburring flash holes.

I shoot only 1-2x/year. I plan to trim cases before separating them by weight of the case plus water to determine the volume of the case before loading them for a 300 yard test. I'm pretty sure I have accuracy load and need to determine the best OAL length.

I don’t weigh in here very often but this is an opportunity to actually share something useful. I will occasionally weigh cases when I have a number of different brands on the bench at the same time just to see if there is a seemingly significant difference. I usually end up brand sorting but there is rarely more that a 1-2% difference (variance as a percentage of total case weight) across them all.
I was really surprised the first time I weighed 22 Hornet cases and found as much as 20% difference consistently between Winchester and Remington cases. The Win. cases were as much as 9 grains heavier than Rem. whose total weight is around 45.5 grains. Older and newer cases didn’t seem to matter much the trend was still there. I think that much difference could make a significant variation in internal volume and then chamber pressure. It’s no wonder I stuck some cases in my Ruger #3 loading 50 grain j bullets with 2400. Your experience may vary, just my $.02 but be careful out there!

JimE said:

I don’t weigh in here very often but this is an opportunity to actually share something useful. I will occasionally weigh cases when I have a number of different brands on the bench at the same time just to see if there is a seemingly significant difference. I usually end up brand sorting but there is rarely more that a 1-2% difference (variance as a percentage of total case weight) across them all.
I was really surprised the first time I weighed 22 Hornet cases and found as much as 20% difference consistently between Winchester and Remington cases. The Win. cases were as much as 9 grains heavier than Rem. whose total weight is around 45.5 grains. Older and newer cases didn’t seem to matter much the trend was still there. I think that much difference could make a significant variation in internal volume and then chamber pressure. It’s no wonder I stuck some cases in my Ruger #3 loading 50 grain j bullets with 2400. Your experience may vary, just my $.02 but be careful out there!

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Thanks for weighing in JimE

This past year I was determined to Try to master my 1911 & this is what I did to greatly improve my groups. Early at the start of last year I was shooting Mixed 45 brass& by switching to one brand In this case R-P brand The groups tightened up a bit.....Then I started to notice that some cases were easier to expand then others! I weeded these lighter tension ones out of my brass I had been using! Things got even better!
I was shooting 25 Group targets and noticed I always had a certain amount of fliers that I was sure I didn't pull!
Then I started weighing the cases........ The ones that were way off amounted to the amount of flyers! Interesting!
I culled those out and then decided to weigh the cases to within +/- .2 grain This then gave me batches of RP 45 Brass that were within .4 grains
As to powder; I weigh every charge within .1 gr and I weigh my bullets to .4 gr
So the before ..... on a 4" bull at 10 yards I was getting about 15 shots in the black and 10 outside of the bull
And the after when I stopped shooting in November ..... on a 4" bull at 10 yards I was getting 25 Shots In the black

Granted I shot my 1911 more last year then the period between 2013 when I bought it and 2020.....so I 'm sure I improved my shooting skills also
but I feel the case discipline was a major factor!
You becha, I'm going to be weighing my rifle cases from now on

Talked to my shooting partner, Steve this morning about weighing cases. He weighs all his cases for competition. He shoots .223, 6ppc and .308. He shot on the Army team many moons ago.

He said he likes to see cases within 1.5 gr. He said Winchester cases tend to have the most variation over other brands. Lapua tend to have the least. Lake City cases are also superb. LC is in reference to .30-06. He gave me 50 LC cases a few years ago. I think I'll run those across the scale and see what I get.

JWFilips said:

so I 'm sure I improved my shooting skills also

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Don't sell yourself short, Jim, it was your improved shooting skills rather than an unscientific experiment.

The only way a difference in weight of SAAMI Spec cases could make a difference is case volume. That extra weight has to go somewhere and it goes to the inner volume of the case. A little bit of difference in case volume can make a significant difference in pressure.
I expect that cases of the same volume would perform the same regardless of weight or head stamp.