How do you separate your cases? Weight or Headstamp?


October 21, 2011, 07:46 AM
In the past I've separated by headstamp but yesterday I started weighing cases and even within headstamp I had weight diferrences as much as 2 grains. I even had cases weigh the same but with different headstamps. The question is how much of a difference is accepatble? I was wieghing LC, PMC and RP. Note that this was after cleaning, resizing, trimming, and primer pocket cleaning.

I know that's a broad question but let's try to keep it somewhere between those whos shoot anything and those whoe shoot extreme benchrest. What would a varmint shooter, or High Master service rifle shooter do?

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October 21, 2011, 08:06 AM
What would a varmint shooter, or High Master service rifle shooter do? Buy new brass of the same lot/brand, prep, load and shoot it. Or sort brass by .1 gr for rifle for best benchrest accuracy. 2gr is not bad as most 243win new factory brass will go around 3gr, rem., win., in lots of 100. You will get flyers that open the group using brass that has a 3gr spread. When you get 2 brass that are the heavest & 3 at the lightest weight, you can see the difference. A rifle chamber has a volume running from the bolt face to where the bullet seals the bore. Any mass of a different weight put into that volume changes pressure. Even with 45 acp match grade Bullseye guns, accuracy can be poor with mixed range brass when your trying to group into 3" or smaller @ 50 yds.

October 21, 2011, 08:17 AM
To a certain existent it would depend if one is a short course or long course shooter in Highpower rifle competition. I use to purchase processed and primed brass from River Valley Ordinance that was mostly Mil-Spec and used it at the 200yd & 300yd lines then at the 500yd or 600yd lines new commercial brass. The commercial brass I did prep. In the past few years I’ve done mostly short course shooting which in my opinion brass prep isn’t required except for trimming to length on a Gracey.

October 21, 2011, 09:19 AM
Both pistol and rifle by manufacturer (headstamp)....was never into benchrest shooting.

October 21, 2011, 10:02 AM
Both if you are shooting a gun that can tell the difference.

General shooting? Sort rifle by headstamp. Don't worry about pistol, mostly.

October 21, 2011, 10:35 AM
My experience has been similar. Keep in mind that unless they are once-fired brass, depending on how many times they have been resized and trimmed, you are going to see variations in case weight. When I bought once-fired .308 cases, I weighed all of them to sort thicker walled less internal volume military cases from thinner walled more internal volume commercial cases. What I found was variations in case weight of several grains even within the same headstamp cases. Between commercial and military cases, weights ranged between 165 to 179+ gr.

Initially, I loaded and range tested from the same weight cases (within 1 gr) but did not find enough differences in shot groups when the case weight variations were within a few grains. I still separate military cases from commercial cases, but OK with case weight variations within several grains post resizing and trimming.

I am not a benchrest shooter, but will "glean" from their practices to produce more accurate loads without going to extreme means. :D

Here are some article excerpts from The Riflemans Journal website, which is dedicated to benchrest shooting, that talk about case prep for precision rifle shooting -

Component Selection
The important concern with your choice of components is their uniformity and how that will affect our twin goals of minimizing variance of muzzle velocity and of BC.

Uniformity of case volume is somewhat important, but incredibly tedious to check. Many people think they can use case weight as a proxy for volume, but it's an unreliable proxy. Weighing cases is a good way to identify a real oddball that got mixed in with your brass (very rare), but the small weight differences some people use to segregate cases are highly unlikely to represent a meaningful difference in internal volume and thus pressure, velocity and ultimately, trajectory.

Case Wall Variance
The more important selection criteria for brass is case wall concentricity. Although this isn't a widely used selection process, I am confident of its importance to higher scores and higher X-counts. [Some] brands of brass, and military brass in particular, are often terrible with respect to this important determinant of accuracy. If you can't check this dimension, at least play it safe by sticking to Winchester or Lapua brass.

Neck Turning
Once the brass is in hand and selected by case wall variance my next step is turning the necks. Now we're getting down to one of those important steps in reducing SD. Neck tension, the case's "grip" on the bullet, is one of the variables that affects muzzle velocity, and necks with inconsistent thickness will not produce consistent neck tension. Neck turning is the solution to this problem and although it can be a tiring process, there's no real alternative.

Other Brass Prep
Apart from selection by wall thickness variance and neck turning, I trim the cases at each loading. This does two things: it keeps the cases at a safe length, because .308 tends to grow quite a bit with each resizing; and the fresh chamfer on the case mouth is a small but important factor in keeping the bullets undamaged and consistent. I also turn the case mouth into steel wool after chamfering to get rid of any remaining small burrs that might damage the bullet - quite likely an excess of caution, but it lets me sleep better. I don't deburr primer flash holes, having found in prior testing that I couldn't see any change from this process. I also don't cut primer pockets to a uniform depth unless a particular lot of cases seems either unusually shallow or unusually inconsistent

Case Sizing
When sizing the case,we're interested in a two main objectives: ease of bolt operation and consistent headspace. I've written quite a bit about the importance full-length sizing as a standard practice ... Consistent headspace is another important element of good long-range ammunition

Primers and Priming
If you want ammunition with single digit SD, you are going to spend a fair amount of time working with primers - unless you happen to get lucky, but I wouldn't count on luck. Once you have the case necks turned, you can begin working with primers. ... Test your primers by shooting each with a standard load over the chrono, varying only the primer. Fire at least 10 and preferably 20 of each primer type. Look for the one that gives the lowest MV and with a low SD although not necessarily the lowest SD (that will come later). That primer should be the one you use as you develop your load, now looking for the lowest SD load by varying powder charge and neck tension. There's a bit of judgment required here, but a low MV on the standard load and a reasonably low SD is the best indicator of a good long-range primer compared to the others.

October 21, 2011, 11:37 AM
If your going to sort brass for the purpose of accuracy, weight is a more important factor over head stamp.

The reason for sorting brass is to attain consistency primarily of internal dimension / capacity which in turn helps to regulate internal pressures. But if your really serious about attaining consistency it is best, and probably easier as well, if you use the same lot # of the same head stamp, every case trimmed to exact same length.

October 21, 2011, 11:38 AM
If I have nothing to do, I will sort by headstamp and then weigh cases. I make sets of 50 and box for future loading. I don't do this until the cases are cleaned, neck sized, trimmed, flash hole deburred, and primer pockets uniformed. Anything that will take metal from the case is done before weighing for obvious reasons.

On cleaning, I also use Stainless Steel pin media as it cleans the inside of the case as well. Unlike the corncob or walnut shell media it doesn't leave any residue from previous firings behind which have varying weights. Even if the amount is small, it is there and there is no way of knowing if it's uniform from case to case.

When sorting a large quantity of brass it is fairly easy to find 50 pieces that are +/- .1 grain, even sometimes the same weight with no variance other than the scale accuracy.

If you really want EXACT cases, don't weigh them, but measure their volume of water. Weigh the case, then fill it with water and weigh again. Record the amount of change in weight which will be the water capacity in grains. This removes all question as to volume.

If merely weighing how do you know that all those cases of the same weight have the same volume??? It's only an assumption where water weight becomes less a guess and more an absolute. The question is whether the time really makes for more accuracy or if one has passed out of the effort/reward zone.

Kevin Rohrer
October 21, 2011, 12:32 PM
Individual rifles get specific makes of brass assigned to them. All other brass gets bagged together until I can find a use for them.

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