sorting by empty case weight?

[JeffG]

I'm not any sort of competitive shooter, but I like finding repeatable precision in all my reloading, for building up my first shot/cold barrel confidence (...I loathed getting the deer-camp nick-name of "two-shots").

My question is; what sort of variance are you allowing when sorting for empty case weights, as a way of gauging consistent internal case capacity?

Thanks for sharing your experience,

 

[dryhumor]

I get a big sheet of paper, a target works well, and weigh and batch them out. Just write the weights you are finding on the paper and cluster together. I’ve found as much as 1-1.5 grains difference between lightest to heaviest, depending on mfr. Those extreme ones become foulers or plinkers. Some brands are tighter in spread than others.

There’s no guarantee that weight difference equals case capacity, but sorting does guarantee a degree of piece of mind. You just have to determine for yourself how wide a weight difference you want to accept. I’m ok with a .2 ish difference or smaller. Trimming and chamfering will remove material, but if the start close, they stay close.

Don’t forget that bullet sorting also helps….

 

[swd]

Buy good quality brass like Lapua. I don't know even a singe competitive shooter that bothers to weigh it.

 

[CharlieNC]

Do a search here and you will find more than you want to know.

 

[Straightshooter1]

I'm not any sort of competitive shooter, but I like finding repeatable precision in all my reloading, for building up my first shot/cold barrel confidence (...I loathed getting the deer-camp nick-name of "two-shots").

My question is; what sort of variance are you allowing when sorting for empty case weights, as a way of gauging consistent internal case capacity?

Thanks for sharing your experience,

I haven't tested by sorting in that way. I have sorted 100 Lapua cases and taken 5 each of the outliers on each end to see what kind of difference in chrono numbers I get. I did get a significant difference in ES's between the two.

Afterward, I when I loaded the sorted cases I kept them in the order they were sorted. The result was very consistent MV's (very low ES's). The only thing I did in terms of measuring case volume was only an initial sampling to find an average case volume using 10 random case selections.

While there is some correlation for case weight and case volume, it's not a uniform thing. Taking a sample size, like 10 or more, you can see that the more the total case weight, the less the case volume and visa versa. But from one individual case to another, you can have a case that weighs more than another and have more volume instead of less (more weight typically means less volume due to thicker case walls).

I find the best use for weight sorting is to identify the outliers. But I do find having batches of brass that are close in weight, produces very consistent MV's (like in my picture below, those weighing from 172.4 through 172.9 grs did really well).

 

[F Class John]

Not everyone will agree but as @swd said, I honestly don't know any competitive F Class shooter who sorts brass but I can't speak to other disciplines. I'm sure it happens, but I've gone down that road several times with several tools to do it with (as have others I know) and it's never led to any conclusive results on target. As a result I haven't sorted brass in at least 7years (including when I won Nationals), but then again I've always shot top end brass like Lapua (but same can be said for ADG, Alpha, Peterson and a couple others). Maybe with range pick up brass there's a benefit but I have no idea. Can it hurt, absolutely not, but you have to figure out what your time is worth for your piece of mind, but in my experience there's way more factors that may lead to a missed first shot than brass sorting.

 

[swd]

And if you’re talking minute of deer accuracy like the OP with good quality brass there is just no reason to sort brass.

 

[TonyinKY]

I sort my brass by weight and culled 10% to get 270 out of 300 pcs for one of my 30BR Long barrels. My velocity extreme spread is usually great but one of yesterday’s shot strings was even better. 2 guns have averaged 2 fps difference between them at times. I use the same load in each with one barrel having 5500+ rds and the other having 1500+ rds. Bullets are Danzac coated. I’ve sorted brass for 25+ years for SR Benchrest rifles and I honestly have never tried not sorting.

 

[monster300]

I have always weighed and sorted cases to 1 grain, because even with the lapua brass in every hundred or so there is one or two that is significantly out of norm or the others. I also weigh out bullets. It is variables you can control before you go to the line. You will see a difference in your SD's.

 

[quest450]

sorting brass by weight for competition is pointless IMO
sorting by internal case capacity makes a lot more sense weather you go with H2O or Bison Armory case capacity gauge it's up to you but that's waaaaaaaay down the accuracy rabbit hole and there is many more important things to worry about especially if you're not competing in LRBR.

 

[JFrank]

Sorting brass by any means has its challenges and none are fool proof. If a guy doesn’t mind using some components then sorting by volocity works well but again requires components and repeating after culling the unexplained . It doesn’t take a masters degree to make a few notes and mark some brass.

Edit to add; I do also sort by weight but just because I feel like it can’t hurt to do so.
Jim

 

[222Jim]

I'm not any sort of competitive shooter, but I like finding repeatable precision in all my reloading, for building up my first shot/cold barrel confidence (...I loathed getting the deer-camp nick-name of "two-shots").

My question is; what sort of variance are you allowing when sorting for empty case weights, as a way of gauging consistent internal case capacity?

Thanks for sharing your experience,

I'm with you re precision.....I'm not a PRS or whatever shooter, but as a retired engineer I want to understand the variables that hurt my precision.

There's an implicate yet erroneous assumption that case weight variations equate to case capacity variations, and it's that internal case capacity that's important in internal ballistics. I've seen for myself that case weight and internal capacity do not correlate. Here are my charts showing my measurements for my .308, .22-250 and .222 cases (note that I've set the case capacity and case weight axis ranges to span 4 grams for consistency):





I've got more data but the message doesn't change - case capacity and case weight do not correlate. But why not? I learned through a Hornady Podcast that the majority of the case weight variation comes from variations in how the case rim is machined, which has no impact on the case internal capacity.

So, I gave up case sorting and only determine case capacity so that my QuickLoad data is better tuned to my situation.

Jim

 

[TTE]

Not everyone will agree but as @swd said, I honestly don't know any competitive F Class shooter who sorts brass but I can't speak to other disciplines. I'm sure it happens, but I've gone down that road several times with several tools to do it with (as have others I know) and it's never led to any conclusive results on target. As a result I haven't sorted brass in at least 7years (including when I won Nationals), but then again I've always shot top end brass like Lapua (but same can be said for ADG, Alpha, Peterson and a couple others). Maybe with range pick up brass there's a benefit but I have no idea. Can it hurt, absolutely not, but you have to figure out what your time is worth for your piece of mind, but in my experience there's way more factors that may lead to a missed first shot than brass sorting.

Two more guys that are 'fairly good shots' will agree with you.

 

[Straightshooter1]

To the question: Is there a correlation between case weight and case capacity?
The answer is a resounding yes! The evidence is clear, like when comparing Winchester .308 brass to .308 Starline brass. If they were mixed together you could separate the case heads stamps just by their weight. And their case volumes are just as different as their weights.

The question is very much like the OP's question. . . how much of a difference in case weights makes a difference in case volumes??? Huh?

When is sorting by weight beneficial? When using high quality brass like Lapua, there's probably not enough variation worth the time and effort to sort them due to lack of enough benefit??? On the other hand, if one is using something like the Winchester brass I happen to have on hand that has more than double the variation, maybe it'd be a good idea to sort them??? Then if one is using mixed lots of a particular brass, I would think that's be a good time to sort.

 

[Bronsin]

Weighing cases themselves doesn't lead to any real answers. You're trying to find the difference in capactiy. If I were to do that, I would take a fired case with the primer still in it, fill it with ball powder, level it off and weigh the charge. That would tell you what you're looking for.

 

[jelenko]

The evidence is clear, like when comparing Winchester .308 brass to .308 Starline brass. I

But that's comparing two different brands of brass.
The question about volume vs weight is within the same brand.

Are you saying the charts shown above are incorrect?

 

[222Jim]

But that's comparing two different brands of brass.
The question about volume vs weight is within the same brand.

Are you saying the charts shown above are incorrect?

The charts are correct for a given lot of cases from a specific brass case manufacturer..............

I made an assumption that someone like me who is interested in precision shooting wouldn't be using assorted brass from multiple manufacturers within a single jump or ladder or whatever test, and/or a mixed bag of range brass..............

 

[prone.life]

I'm not any sort of competitive shooter, but I like finding repeatable precision in all my reloading, for building up my first shot/cold barrel confidence

Sorting brass won't solve your cold bore issue (or any other issue imo). Best way to predict cold bore accuracy is recording / making note of cold bore performance each range visit; some call it DOPE.

 

[Bottom Fodder]

Cold bore shot = buck fever

 

[Straightshooter1]

But that's comparing two different brands of brass.
The question about volume vs weight is within the same brand.

Just because the different brands doesn't matter, the math is the same as the exterior dimensions are the same.

Are you saying the charts shown above are incorrect?

No, not saying they are incorrect at all. In fact, they still support the hypotheses for the correlation between weight and case volume. Though I don't have the actual raw data to draw the slope, I can still draw an estimated slope of those data points where you can see the relationship for weight and volume.

And BTW, it would have been better data had the weights no include the primers as the primers have some variance too; as well as the data being a small set.