Grouping brass by weight

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fatboyz

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I'm going to the next step with my reloading and want to seperate brass by weight. What parameters should I use to seperate them? How many grams or grains should I seperate them by. Can you mix brands if they fit into the same weight step? If I'm using say Rem brass, how much dif is there in weight from case to case and how much of a dif does it make? Basically what I'm trying to figure out is if I have say 200 Rem brass (7mm Rem Mag) how many of that 200 can I expect to be within useable tolerance weight wise?
Do I keep looking for more Rem brass that fit into my "chosen" weight category?
Don
 
Sorting cases.

PLEASE, explain to me how you sort for capacity [VOLUME]. Is that like the 223 vs 300WM.

If you want to sort by weight, complete all the prep work of the brass first.
2 to 3 grains is not going to make any difference. I wouldn't bother unless it makes you feel more confident in a big shoot.
Bill
 
Weight sorting is a waste of time but if it makes you feel better have at'er. Like Ian said volume would be more meaningful and even that is a bit overboard IMO. If I was to weigh anything other than powder it would be bullets, thats it.
There are some people on this forum that weigh this and that down to primers. I think for most people including precision, f class and BR guys there are more important things to do with your brass than weighing it. Proper brass prep including doing primer pockets, flash holes and neck turning would be far more important than weight sorting.
Ivo
 
I sort my .308 Win into lots based on rough groupings and often find that I can get plenty of cases within +/- 0.1gn in approx 174-178gn case weights, differing by manufacturer. The most I ever got in a lot of 100 was 72 in +/- 0.2gn with 54 +/- 0.1gn. Most of my Lake City comes out in the 176-178gn range, with the commercial loads coming in 174-176gn.

After the initial weight sort, I then fireform using Bullseye and Cream of Wheat with a toilet paper and wax plug (sometimes just the toilet paper) and THEN I get to sorting by case volume. Water with a little isopropanol does the trick, since the iPr-OH breaks the surface tension a bit. Soap would do the same, but you might have bubbling issues.

A sort like this lets me know I've got uniform case capacity AND uniform wall thickness, on the whole. Overkill? Maybe. But I need something to do during the winter if our range is snowed in, don't I?! :D

And any cases outside my 'normal sort' range get tossed in the OAL gauge pile or become plinking/short-range hunting cases - or given to friends with the warning that they're "rejects" from my best-sorted case lots.

-M
 
Use one brand of brass from one lot. That way you get the same alloy and hopefully the same case dies and annealing program.

Weighing cases is a waste of time because it doesn't tell you what you want to know.

It was an 'easy' way to get a comparative value for CASE VOLUME. Easier then filling cases with water to confirm volume.

The assumption is that if the weighs of the cases vary, it must mean the volume is different. Big flaw in this assumption is the milling of the extractor groove. They can vary substantially from case to case and it doesn't take alot of brass to vary the case weight.

Don't believe me - take this test. Fireform a batch of brass then Weigh and separate in whatever groups you want. If you are concerned about the weight that the powder residue may leave, weigh into groups THEN fireform. The act of firing brass will change its case volume but will equalize the cases in that batch shot in that one rifle.

Take a very fine grain gunpowder like Win680 and fill one case to the brim (trim all cases to the same length) tapping the side to ensure it is full and settled.

Now dump into the next case and see how much it fills. It will overfill at first but after tapping will settle down to be right on the case.

Take a case that is out of the weight range and repeat. I bet it will also measure bang on. I consider a variation of volume HEIGHT of 1/16" equal.

I have done this test on a wide variety of brands and chamberings and have had the same results. Case volume varies very little to none in that one lot but case weights can range a few grains.

How much does an extractor groove affect your groups???

Another test, take the same weight of cases but from different brands or lots and do the volume test. You may find that the volumes don't match up even though the weight does.

Enjoy...

Jerry
 
how much powder are you guys using for fireforming. I have a few cans of red det kicking around. Will that work. Also LR primers are much easier to find here that LRM primers. Can I use the LR for the fire forming?
Thanks.
 
First off Don, what is it you will be using the brass for?
Competition or group shooting at your local range?

I use my brass for competition so I want as much uniformity as I can without spending a boatload of time where it is unecessary.

I weight sorted my Lapua brass into one grain "lots"

600 Cases weighed (2 lots of brass....400 from 1 lot and 200 from another), 450 in one group (126.0-126.9grns), 125 in the other (127.0-127.9) and 25 that were either above or below the 2 weights which are still in the lapua box.

I guess I should sort by volume instead. Might help my shooting. ;)

I do agree with Jerry on the same brand, same lot if you are going with Rem,Win,Fed, etc....
 
If you are using Lapua brass, sorting by weight is useful and this is practised by most longrange shooters seeking best 900 metre accuracy. there is a relationship between performance and weight.
 
I know I'm going to get stomped for disagreeing with Obtunded and Mystic, but IMHO, if you sort your brand new untrimmed, non-uniformed, brass by weight prior to neck turning or reaming, and provided that all that brass comes from the same manufacturer and case lot, you are sorting by volume. Once you have trimmed and uniformed primer pockets and flash holes, and turned the necks, then I agree, there is no way of knowing what it is you are weighing. Once the brass is sorted into groups, there is no need to move it from one group to another throughout its life.

As for whether or not it is a wast of time, when shooting at extreme long range or when shooting in competition, if you can measure it, it matters, and if sorting brass into groups of +/- .5 gr makes you feel better, even if the results on the target don't necessarily show any difference on any particular day, then it is worth it. With an electronic scale it doesn't take very long. If you believe there is a variable you can control, and you control it, that will make you more confident of your ammo, and confidence wins matches. Consider that a difference of 25 fps will produce a vertical spread of 2" at 1000 yards, and keeping the extreme spread of your ammo's velocity to single digit variances requires a high degree of attention to detail, and a uniform velocity spread is but one element of what makes accurate ammo.
 
Take one lot of brass and seperate by weight. Then take the heaviest 5 pcs and the lightest 5 pcs within the lot and compare volumes of the 2 groups. You will see that there is little relationship between the weight of brass and the volume within the same lot.
 
Since brass is elastic, I don't see how measuring the volume of fired brass outside of a chamber has much to do with anything. The only reason you can even get the brass out of the rifle is because it contracts from the chamber walls after firing. And this elasticity is not uniform.

The steel chamber determines the volume under firing pressure, not the brass cartridge case. Even that volume is suspected to vary, because the chamber will also expand under pressure, and not exactly the same every shot.

Measuring the volume of fired cases would be a lot of work with no meaningful results. If you must sort your brass stick, to weight sorting. Ie: heavier brass occupies more space in the chamber, thereby reducing the total volume available for combustion under pressure.
 
I have sorted by weight. out of a 500 lot of Federal GM brass, I got a range from 176-178 grain for the most part and seperated it into +/- 0.25grn lots. 176.0-176.5 etc.
I wouldn't say it had a huge impact on goups, it did seem to keep the flyers down a bit.
I think weighing and comparator checking the ogee on all you projectiles would have a bigger impact.


Out of curiosity I check some winchester made brass and found it to be 10 grains lighter per case, in the 160's.

JT.
 
rpollock said:
Since brass is elastic,.... And this elasticity is not uniform.
Click to expand...

I disagree. Brass has a very reliable elasticity which is why we can get consistency in neck tension. Why we can size cases to fit with zero headspace.

Just measure the outside dimension of your fireformed brass. I bet they will vary no more then 1 thou (which is typically the error rating on most calipers).

At least they should if the lock up is tight and chamber concentric. They certainly do in my rifles.

As long as the ammo formed from any brass prep procedure gives you the performance desired, it's all good.

Personally, I have found weighing powder charges and maintaining my neck tension to have a larger effect on target then any other area of case prep.

Jerry
 
mysticplayer said:
I disagree. Brass has a very reliable elasticity which is why we can get consistency in neck tension.

Jerry
Click to expand...

I haven't seen this very reliable consistency you talk about. High pressure loads will reveal this weakness in elasticity straight away (I know you advocate low pressure loads, so maybe you haven't noticed this) some brass will pop open and others won't in the same batch using the same load, this variance is due to the elastic limit of the brass having been exceeded in some cases and not others. This is a variance in elasticity.

Immediately some cases will start to work harden faster than others, and neck tensions will start to vary after a few firings. You can feel this using straight line seaters and arbour presses. After repeated firings, say in a batch of 10 cases 1-2 will start to vary in neck tension. This is a variance in elasticity.

One other point, trying to measure volume using trickled powder would be futile. I can vary how much powder a case can hold just by varying my technique a little, probably about an extra full grain of powder can be put in a PPC just by using a slow pour, a long funnel, and some tapping. How can you be sure the variance in case volume you are getting is not just an inability to pour or pack the powder the same every time? You can't, nobody can, which is people are switching digital scales to measure charges, not volumetric throwing.
 
rpollock, you are right in that I don't try and shoot using pressures above 65,000psi so I am below the yield or elastic limit of brass. Having read some tests showing how powders can get real screwy in the upper 70 to 80,000psi range, you may be seeing enough PRESSURE variance which shows up as different degrees of brass 'failure'.

Powders do not always react well at proof pressures. They were never designed to work at those levels.

The elasticity of brass is constant within an alloy batch (just ask any metalugist/engineer) but the pressures it experiences during the firing process can vary widely (when you get over 65000psi). I have certainly experienced this with over pressure loads. Things get real exciting real fast even with very small changes in powder increments when right on the edge of pressure.

One case will show extreme pressure signs, another will blow the primer. At these levels I don't blame any component, just the guy pushing the throttle open too far.

There are several ball powders with a charge density that is pretty close to 1gr/CC or essentially 100% load density. I use Win 680 and if you have seen this powder you will understand what I mean.

It is fine enough to JAM up some powder measures by getting between the drum and the measure. That is pretty darn fine.

As I described in my description above of my technique, I most definitely tap the case until it settles as much as possible. When you pour into another case, it overfills but settles down with tapping.

Can there be error in this method, sure, but we are talking very small levels and well within anything that has affected my groups at either short or long range.

The use of scales has everything to do with how powder measures NOT work with extruded powders. With bridging, you can get all manner of charge weights so that affects the effectiveness of this load.

If you were to measure these charges, the weights would also change. Extruded powders, even something like Benchmark will not pack tightly enough in a powder measure for volumetric measurement to work.

However, use them with ball or flake powders and the charge weights become quite consistent so more a problem with the mismatch of powder and tool.

I have mentioned this several times in the past and have received some colourful comments from some SR BR shooters exclaiming how they have used it for decades with more then satisfactory results.

Nice to see that techniques can change and groups can shrink even more.

YMMV,,

Jerry
 
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