Why sort cases by weight?

[VaniB]

The more uniformity a handloader applies in the reloading process, the more consistent the accuracy should be. This is why I carefully weigh powder, uniform the primer hole, anneal the brass to control neck tension, verify uniform AOL, and sort cartridges by their final concentricity. I also sort bullets by their weight, because any difference with the bullets can effect the flight and POI onto the target. But a case doesn't fly downrange. The powder capacity and combustion of 26.4 grains of R15 remains the same regardless of case weight. I also really can't see the logic in it making more sense for 1000 yard shooting then for 100 yards, as the same logic dictates to me that a nothing burger shouldn't make a difference at expanded distances if it doesn't exist.

I will not challenge your explanation if you have one. I'm just trying to make sure I didn't overlook something.

 

[Ned Ludd]

Burning powder is a chemical reaction. Chemical reactions are very sensitive to pressure, which is determined by the volume of the pressure cell (combustion chamber) in which the reaction takes place. In other words, the internal volume of the case, which has expanded out to the limits of the chamber dimensions, affects pressure, and therefore the reaction rate. Because the internal chamber dimensions limit the expansion of the brass, fired cases have very uniform external dimensions; the only possible sites of variance being in the extractor groove and primer pocket. The thinking is that if the external dimensions of a fired case are uniform, variance in the brass thickness in the case head, wall, shoulder, and neck regions will directly affect the internal volume of the case, proportional to the difference in the thickness. Therefore, sorting cases by weight is a method used by some as a quick and easy surrogate to determining actual case water volume, which is much more laborious.

In my hands, the correlation between case weight and case volume is really quite good, not perfect mind you, but very good, so I sort cases by this method routinely. Nonetheless, others have a different opinion, and threads such as this often elicit arguments over whether case weight can effectively be used as an estimate of case volume for sorting purposes. You will have to decide for yourself whether you believe case volume is proportional to case weight.

 

[dcali]

What he said^

If you’re wondering why not measure volume directly, you almost can- by using the weight of the water it takes to fill case (water is incompressible, so weight is proportional to volume). But this is tricky and time consuming. It’s *much* easier to sort by weight. Threads on water capacity measurements also tend to get bogged down in opinions over finer points of the technique and whether or not it’s worth the work involved.

 

[Mulligan]

Look closely, you can see the ink on the paper inside the bullet holes.
Red was the lightest 5 cases in the box
Blue was the heaviest 5 cases in the box.
284 win/Norma brass/180 Berger hybirds/powder measured on FX120i/600 yards


CW

 

[59FLH]

If you control the OD and length of a cartridge case by trimming, sizing or chamber firing, etc., you can assume the internal capacity's are the same if the weight is the same, AND the material is the same, it's a simpler way to volume sort than cc'ing each and every case. Why? For the reason Ned posted in #2, internal volume effects pressure.

The truth of the matter is SAAMI only controls the outer case dimensions, the differences come from the base and wall thickness variation, the only way to really know is measure the volume. BUT, if you get that far into the weeds with this stuff, you will spend you time dicking with your cases and never get to shooting.

IMO a hundred practice rounds fired down range will make you a better marksman then one grain of case weight ever will.

 

[foxguy]

Burning powder is a chemical reaction. Chemical reactions are very sensitive to pressure, which is determined by the volume of the pressure cell (combustion chamber) in which the reaction takes place. In other words, the internal volume of the case, which has expanded out to the limits of the chamber dimensions, affects pressure, and therefore the reaction rate. Because the internal chamber dimensions limit the expansion of the brass, fired cases have very uniform external dimensions; the only possible sites of variance being in the extractor groove and primer pocket. The thinking is that if the external dimensions of a fired case are uniform, variance in the brass thickness in the case head, wall, shoulder, and neck regions will directly affect the internal volume of the case, proportional to the difference in the thickness. Therefore, sorting cases by weight is a method used by some as a quick and easy surrogate to determining actual case water volume, which is much more laborious.

In my hands, the correlation between case weight and case volume is really quite good, not perfect mind you, but very good, so I sort cases by this method routinely. Nonetheless, others have a different opinion, and threads such as this often elicit arguments over whether case weight can effectively be used as an estimate of case volume for sorting purposes. You will have to decide for yourself whether you believe case volume is proportional to case weight.

Ned,

I have been wondering when weighting cases if the cases are trimmed to a uniform length first?
What if any case prep is done before case weighting?

Thanks

 

[AJC]

Ned,

I have been wondering when weighting cases if the cases are trimmed to a uniform length first?
What if any case prep is done before case weighting?

Thanks

Sorting should be done with completely fire formed and prepared cases to ensure dimensional consistency.

 

[Metal God]

I’m not sure you all are giving the full story .

Let me ask you this , is case weight directly proportional to case volume period? No caveats , if’s , ands or buts ?

I believe I know the answer to this since I’ve weighed and checked case volume on multiple brands of brass over multiple manufactured years .

I can say with confidence that case weight is not directly proportional to case volume , full stop . Now if you want to say it’s proportional when using all the same brand and lot of brass then maybe I could get on board . However that would bring in some if’s ands or buts rather then the blanket statements that appear to be in this thread .

If sorting by weight was directly proportional to case volume there would be no need to separate by manufacture ????

 

[Uncle Ed]

Why sort cases by weight?

Because it is faster than filling each case with water and checking the case capacity.

Some of us just don't like waterboarding our cases.

 

[JMayo]

Why sort cases by weight?

Because it is faster than filling each case with water and checking the case capacity.

Some of us just don't like waterboarding our cases.

LMAO !

 

[group therapy]

Why sort cases by weight?

Because it is faster than filling each case with water and checking the case capacity.

Some of us just don't like waterboarding our cases.

 

[group therapy]

The more uniformity a handloader applies in the reloading process, the more consistent the accuracy should be. This is why I carefully weigh powder, uniform the primer hole, anneal the brass to control neck tension, verify uniform AOL, and sort cartridges by their final concentricity. I also sort bullets by their weight, because any difference with the bullets can effect the flight and POI onto the target. But a case doesn't fly downrange. The powder capacity and combustion of 26.4 grains of R15 remains the same regardless of case weight. I also really can't see the logic in it making more sense for 1000 yard shooting then for 100 yards, as the same logic dictates to me that a nothing burger shouldn't make a difference at expanded distances if it doesn't exist.

I will not challenge your explanation if you have one. I'm just trying to make sure I didn't overlook something.

and it helps some of us to sleep better (you also have to remember that we, as br shooters, are eliminating variables. as many variables as we are prepared to attack. I, for one, am not drilling kernels). and clays post . and the difference in long range vs short range is significant

 

[dsculley]

I can't remember his name, but there was a guy from Lapua who said on a thread there is no correlation between case weight and case capacity. If I recall correctly, he said the case is formed around a mandrel so the capacity is pretty consistent. The weight difference is usually in the case head. I use primarily Lapua brass. When I get a new batch, I will pull 10 from a box of 100 and measure the case volume with water. I have not found enough variation to warrant further testing.

 

[group therapy]

View attachment 1144247

Look closely, you can see the ink on the paper inside the bullet holes.
Red was the lightest 5 cases in the box
Blue was the heaviest 5 cases in the box.
284 win/Norma brass/180 Berger hybirds/powder measured on FX120i/600 yards


CW

and there you have it

 

[sdean]

and there you have it

Correct although only one sample. The segregated groups were half of the combined.

 

[AJC]

I’m not sure you all are giving the full story .

Let me ask you this , is case weight directly proportional to case volume period? No caveats , if’s , ands or buts ?

I believe I know the answer to this since I’ve weighed and checked case volume on multiple brands of brass over multiple manufactured years .

I can say with confidence that case weight is not directly proportional to case volume , full stop . Now if you want to say it’s proportional when using all the same brand and lot of brass then maybe I could get on board . However that would bring in some if’s ands or buts rather then the blanket statements that appear to be in this thread .

If sorting by weight was directly proportional to case volume there would be no need to separate by manufacture ????

Sorting by manufacturer accounts for wall thickness and demionsonal head differences

 

[Baddog0302]

Other than " stool shooters " shooting BR at 100 & 200 yds. At what ranges does this start to make a difference ? 600 ? 750 ? 1000 ?

 

[rsmithsr50]

i like it when people do not weigh cases, I move up the finishing order.

 

[Metal God]

Sorting by manufacturer accounts for wall thickness and demionsonal head differences

As well as the 80/20 or 70/30 percentage of materials used to make the brass . Then there's the question are all one manufacturers brass made on the same machine ? Different machines can create different brass in this context . Meaning just cus it says Lapua doesn't mean your GTG with weight . We all know this when it comes to Winchester brass . I've seen as much as 15gr differences in Winchester brass and have heard of as much as almost 30gr differences .

My over all point is very narrow and really is going to the new guy that comes along and thinks weighing your cases will result in a direct correlation to case capacity consistency , it simply does not . This is not to say weighing your cases does not help at all , I'm not saying that . Can you weed out a few bad apples by weighing your cases ? Sure , but it does not mean now all those cases you've separated now have the same internal case volume .

My guess is you guys that are weighing your cases and seeing correlation are likely using high end brass with the same lot number ????

 

[Lonestar41]

If you control the OD and length of a cartridge case by trimming, sizing or chamber firing, etc., you can assume the internal capacity's are the same if the weight is the same, AND the material is the same, it's a simpler way to volume sort than cc'ing each and every case. Why? For the reason Ned posted in #2, internal volume effects pressure.

The truth of the matter is SAAMI only controls the outer case dimensions, the differences come from the base and wall thickness variation, the only way to really know is measure the volume. BUT, if you get that far into the weeds with this stuff, you will spend you time dicking with your cases and never get to shooting.

IMO a hundred practice rounds fired down range will make you a better marksman then one grain of case weight ever will.