Are the differences in casing weights of used (at least once fired) cartridges more likely to be the result of manufacturing tolerances or changes resulting from multiple usage (age cycles)?

Using a new Frankfort digital scale, I've been somewhat surprised at the min-max differences and STDEV in weights from the various manufacturers. Not so much that there are differences between the mfg's, but rather the differences in casing weights with the same headstamp.

Starline and Winchester appeared to be the most precise (STDEV's at 0.25 and 0.74 grains respectively for 9mm brass), but I'm wondering if that may be the result of those in my sample population being my newest brass. Had they been fired the same number of times as some of the others, and been subjected to the same number of cleanings and other exposures, would their STDEV have been comparable? Federal and R-P appeared to be pretty terrible; like up to 2 grains weight differences between cleaned and primed cases.

I was thinking that I could use completed cartridge weights to identify under or over-thrown powder weights, but with such disparity, even with segregated headstamps, that method doesn't appear to work.

I'm curious what others have seen with regard to case weights and what, if anything, it can tell us. Do cases loose weight with each firing cycle (erosion/wear); are the differences more the result of cleaning differences (clinging media residue); or are the weight differences just what would be expected from the mfg process?

Life was sure simpler with my old single stage press and single beam balance. -S2

I can't remember where I saw it but 2 grains of brass is such a small amount of material it's like the equivalent to a fraction of the size of a piece of powder. I'd be more concerned about differences in case wall thickness of various manufacturers before I'd worry about that.

Same old, same old. You'll never notice the difference. Even if there is a slight difference, the guns aren't accurate to tell any way.
I have run sorted cases by weight, by head stamp, and mixed (using cases that didn't match anything else) and the mixed were always just slightly more accurate (except, running a t-test, they were statistically "the same" at 9% fiduciary level.
It isn't going to hurt if you want to spend time sorting by weight or head stamp, though.

I sort all my brass by headstamp, that's as far as I'm interested in going. You have to be the one comfortable in your reloading practices, so do what you feel you need to do. I've actually been trying to shoot misc. brass, but I prefer to load all one headstamp-goes back to my PPC days when I was meticulous about my competition ammo! Some habits are just hard to break! LOL :-) Used to weigh all my bullets, though; but never thought of weighing the brass-it all got trimmed though!

I found it much easier to sort brass by caliber. There is no need to weigh the cases. Powder and bullets are usually weighed. Powder to verify the correct charge setting on the powder measure. Bullets to verify the correct weight per product label.

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S&WHF 366

I've seen considerable # of serious reloaders attempt to establish some kind of 'range of brass-ness' per weight, in combination with water volume, case head stamp, lot #, total reloads on that particular brass, trimmed to spec OAL brass, loaded with all head stamps aligned to some imagined Best Point.

While I do see the effects in the group, self-admitted or not, considerable sign of OCD/CDO/whichever, and have heard various theories about 'the Brass'.....there has never been a coherent or widely disseminated theory about just what effect 'coherent matching brass' would have on measurable accuracy....especially in the face of so many OTHER variables.

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Dum vivimus Vivamas

If I get a flyer or two, I just blame it on the guy pulling the trigger. Life is so much simpler that way.

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Some collect art; I shoot it!

I gather you are talking about pistol brass. I've never found a reason to weigh pistol brass, but I have to assume the factors are the same as for rifle brass.

The major weight differences between *quality* rifle brass are due to the thickness of the walls, the density of the rim area, and perhaps the specific alloys used.

Beyond those there are differences based on that manufacturer's degree of control over the manufacturing process of that batch of brass. As you've apparently found, some manufacturers can be better than others . . . eg Lapua's reputation for quality, consistent brass.

The weight of a brass case will change slightly if trimmed, but I've not seen any change in mass due to firing or tumbling. Then again, none of us has seen it all lol.

It is possible to use cartridge weight to determine if you've got a cartridge with no powder . . . but only if the target powder weight is so large it can overcome the variation in case and (yes) bullets weights. Weighing most pistol rounds with eg 5gr powder loads will leave you uncertain at best.

FWIW, the most consistent factory ammo I've seen is 168/175gr FGMM 308 ammo . . . IIRC the 175s weighed 400gr +/- 1gr. If one had no powder, you'd know it

The difference in weight of brass of the same caliber/different headstamp is due to manufacturing not number of reloads.

Even some brands of brass of the same lot will vary. more so with rifle brass (there is more of it)

No, weighing loaded ammo will not tell you anything. The bullet will vary more especially in smaller handgun calibers.

Now if you load something that holds 20 grains or more you will probably notice if one is empty.

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Still Running Against the Wind

In 60 years of reloading I've never been able to figure a way to weigh the completed cartridge to determine a double charge. There is and always has been way too much variance in the brass itself.

Internal case capacity is more important than case weight since it can affect the pressure of the round. I would submit that not even the best handgun shooter could tell the difference in group size as it relates to case weight. Now, in benchrest rifle shooting case weight relates as one of the finite things those guys consider.

I spent a little time last Saturday morning weighing and determining H20 capacities of various 9mm casings and found that 9mm brass can weigh anywhere from 52.8g (Blazer) up to 62.4g (FC) with as much as 4 grains different within the same headstamp (FC), although most are within 1 grain.

I did this because I wanted to see what were the effects of case volume on the MV and Pmax in Quickload. The spec volume of a 9mm case is 13.3g H20. My fired cases averaged closer to 14.1g meaning the pressures are quite a bit lower and the MV's will also be lower in real life than predicted which they are when I measure them on a chrony.

Back to the cases.
The measurements also verified that weighing loaded rounds will not catch a double charge unless you measure all the same headstamps and in some cases, it won't help there either. If you ever suspect a double charge, grab the bullet puller and have yourself a pulling session. After all, is your gun and hands worth the extra time and effort? Most components can be reused anyway.

well aware of it ... it's manufacturing runout and makes weighing loaded cartridges to confirm powder charge an exorcise in futility.

It has little to do with age, or use. Matter is neither created nor destroyed.
Thus, a case being matter remains unchanged in terms of weight even if you liquefy it.

cases do not fail due to wear and erosion. they work harden until they crack. You'd be lucky to detect any change with the instruments we have.

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it just needs more voltage

I always sort my brass by headstamp and I'm not OCD. I do it to reduce disparities in case length and internal volume.

Many years ago I made a batch of 45ACP with 5.6gr of 231 and 200gr LSWC. About 1/3 of the 500 round batch had no powder(don't ask). So I tried weighing rounds to sort out the squibs(all same headstamp, primer and bullet brand). I can testify here folks...that method absolutely doesn't work!

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Bob.
SWCA 1821

I used to weigh rifle cases back when I shot competitively . The thought was that same internal volume was ballistically more stable . Back then the most consistant were Norma & Lapua . They also had drilled flash holes & machined case heads . Cost a hell of a lot more too . Also when uniforming primer pockets very little work was needed . Case dimensions were also uniform . When shooting 600yds or more it paid off . Think that's anal , look at what benchrest shooters do for case prep . Handgun cases it doesn't make any difference at all . With lead bullets & mixed cases there was practically no difference . Jacketed bullets the same lot / headstamp does make a small difference in groups @ 50yds . With 9mm especially .

Why not have some confidence in your reloading techniques and shoot your ammo through your gun across someone's chronograph ? You will then know what the ACTUAL bullet velocity is, and quit worrying about statistical and formulae nonsense. Just pull the trigger, that's why you loaded the ammo.

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S&WHF 366

weighing pistol cases=OCD/waste of time= not necessary for 99.9 % of us with normal handguns shooting at 25 yards or less. But do what makes you happy. Variations in velocity attributed to case volume are just too small at 25 yrs or less, they become mixed in with varations in the projectile weight, variations in seating depth that effects volume. Just a huge waste of time.

Rifle brass=yes in particular when shooting at longer 300yds +

In fact I do run these across a chrony and I do have confidence in my loading techniques. What I was trying to do was to check confidence in Quickload and see if/where real loads might diverge from predictions.

I performed 2 chrony sessions this week. The first was with BE-86 loading at 4.8, 5.0 and 5.2g each with 10 shot strings. The 5.0g load was the best @1136 although my SD's went down as the loads went up implying there was still some room for improved burn. I should be able to go to 5.8g and get close to 1270 fps, but I'm sticking with 5.0 because it gives me the target 1100+ fps needed to get good case ejection. No need to batter the gun with a hotter load or stress the chamber with more pressure than necessary.

The tricky situation in pressures comes with Titegroup. I've loaded anywhere from 3.8g to 4.4g and got velocities ranging from 1027 to nearly 1200 fps. 3.9 gave me excellent SD's of 6.9 fps, but with only 1050 fps, the cases flipped up about a foot and often hit me on the head or flew into my forehead. Accuracy was fine, but the cases are a distraction. 4.2g ended up being the best load, but theoretically (there's that naughty word for "engineer's" again) that is over pressure unless you increase the case volume from the spec 13.3g H20 to 14.0g H20. In that instance, the Pmax is only 30,800 psi instead of close to 36,000 psi. Is a +P load going to cause a kaboom? No, but it's more comforting to know that I'm actually not reaching that pressure with this powder. In fact 4.4g should only reach 34,000 psi instead of the 38,400 caused by a 13.3g H20 case.

I'm sitting on an 8# jug of this stuff and I want to know if this is OK to use for the next year's worth of shooting. I already know it's acceptable in 40 S&W, 45ACP, light 38 special and 12 guage slugs (I still need to test out loads for skeet and trap)

When I got off the chrony, I shot some straight offhand. 10 yard groups were not bad. I'm not a great shot, that's why I reload. There's no way I could shoot enough to get better if I didn't reload. The small holes are from my SW22A-1 just to warm up with some trigger control exercises.


So, yes I do pull the trigger to make my gun go "bang" about 200-400 times a week. Over the past 4 years about 40,000 rounds, mostly 40 S&W but more recently with a lot of 9mm with the S&W 9mm barrel in my M&P 40, a Shield 9 and 92FS.

I agree that weighing pistol cases are a waste of time if you do it all the time. I simply wanted to know what variations there are. As with 9mm guns, 9mm ammo can be all over the map.