Best way to sort brass?

[Bart B]

Bart B, thanks for responding, but my question is not answered.

Is this your question?

If this is true, it is only necessary to sort a batch of cases by weight and not by volume.
Is there anybody with more knowledge about this who can sceintifically confirm my view?

I've shot sub 1/2 MOA (under 5 inches or 12.7 cm) 15-shot test groups at 1000 yards with two different 30 caliber magnum loads using cases sorted to a 1% spread in weight about 230 grains.

And 20-shot group at 800 yards under 4 inches (10.2 cm) from a .308 Win. with cases sorted to a 1% spread about 157 grains.

The most accurate (smallest) string of 10-shot groups ever made (as far as I know) were done with cases sorted by weight to a 1 grain spread of .308 Win. cases averaging 150 grains. Several groups were all under 1.5 (3.81 cm) inches and the smallest down to about 0.7 inch (1.78 cm). And a 40-shot group measured 1.92 inch (4.88 cm).

This is as good as anybody has shot anything with anything sorted anyway for the numbers of shots fired. I make no claim that it's scientific, but it's pretty close to being so.

Personally, I think it depends a lot on how one tests the results of different case sorting criteria. Some folks will get good results with any method.

 

[Pieter Willem Vorster]

Actually my question is: "... if you have two cases, A and B, with the same outside dimensions and made from the same alloy, and the weight of A=weight of B, the volume of A=volume of B."

Is this true?

 

[Greyfox]

I just went through a situation with my 260 which I used Lapua brass. Norma brass was within 2 graings wt. the Norma case was 1-2 thousandths smaller above the base. Velocities, POI, and accuracy o.25-.36 MOS was identical for both fired and new brass.

 

[Bart B]

Actually my question is: "... if you have two cases, A and B, with the same outside dimensions and made from the same alloy, and the weight of A=weight of B, the volume of A=volume of B." Is this true?

Yes. With equal amounts of brass, the volume of each is equal. The less brass there is inside the chamber, the more room there is for powder. At peak pressure when the case is pressed hard against the chamber and bolt face, lighter cases have more space inside of them.

Some folks feel the case volume before firing is more important.

 

[Joe King]

Actually my question is: "... if you have two cases, A and B, with the same outside dimensions and made from the same alloy, and the weight of A=weight of B, the volume of A=volume of B."

Is this true?

Generally yes, provided your using brass of the same make and lot. Other wise you can run into variances in the head of the case which "can" throw things off. Just like everything else with reloading "It Depends" is still a best fit answer

 

[MNbogboy]

A while back I did a small test with a small sample of twice fired, cleaned, sized & trimmed cases.....The weight vs volume test was done on the heavy three & light three cases of a 50 case lot with 3.5 grains of extreme spread....

These were Remington brand 25-06 cases expanded and fire-formed to 6.5-06....Volumes decreased in 5 of the six cases as weight increased (as expected)...With one exception the heaviest case had more volume than the lightest case!....I checked this three times....My conclusion was the brass distribution within that case was quite different than the others....In other words the internal shape may vary even in cases that weigh the same...As an after thought I wish I would have "sliced" the two extreme cases lengthwise and made measurements....

Granted this was one test and one instance but may be another reason to explain unexpected "fliers"...Even in complete volume tested cases....I would also have reason to believe that manufacturing processes could explain what I found and that "better" more expensive brass could have a better handle on this.....

Personally I normally weight sort only after two firings and sizing, cleaning and trimming...plus or minus 1 grain...But my best sorting method is"placement in the group" during a session at the range using a sharpy on any suspect case heads and watching them on subsequent firings....Twice out of the ordinary unexplained results usually get them booted....I had at one time an electric tool etcher that I numbered every case in a lot....It was a lot easier to keep track of "bad eggs" back then...Maybe I should buy another one...

My $.02,
Randy

 

[Bart B]

But my best sorting method is"placement in the group" during a session at the range using a sharpy on any suspect case heads and watching them on subsequent firings....Twice out of the ordinary unexplained results usually get them booted

Is your rifle's bolt face squared up with the chamber axis?

 

[Pieter Willem Vorster]

Thanks for your inputs.

Regards

P.W.V.

 

[MNbogboy]

Bart & Pieter,
Yes, if external dimensions are exactly the same and the brass has the same density then weight sorting is perfectly accurate for volume only...

Weight sorting is my method of choice but obviously not fool proof...

One variable not affected by fire forming is the rim/extractor groove...This is an external dimension controlled mainly by manufacturing processes as mentioned earlier and normally not affected by fire forming...
Therefore any addition/subtraction at manufacturing to this area will affect case volume and/or internal dimensions if the case weight remains the same...

As Bart mentioned even barrel/bolt alignment could be a cause for erratic case weight/volume relationships...
But this also would affect the external dimensions of the case and obviously skew test results.

Also mentioned earlier was the fact that "cheaper" brass may be suspect to quality issues...I have had brass in the past that would not even slide into a shell holder...My guess would be that these areas may or will not be totally uniform in some or any cases (no pun intended).

For the above reasons case volume sorting alone nor weight sorting nor a combination of them both may not answer every problem...
There will always be the possibility of two cases weighing the same and with equal volumes that shoot different...
We can only speculate that maybe the distance to the primer may be different or even the internal shape of the charge is different, most likely due to
differences at the rim/groove...

Food for thought,
Randy