Weighing cases?

[encoreguy]

How much variation do you accept when you divide into weight groups. Due you use + / - .5 grains for a total of 1 grain variation or what is acceptable to you?

 

[billmo]

Most guys that weigh cases will separate into groups of .5 gr to 1.0 gr. Bill

 

[SlowpokeRodriguez]

Good question but how do you know when weighing cases that where the weight differential is will effect case volume? Point is you can't so to make this type of activity worthwhile you would have to check each cases volume individually.

Think about it. Believe me if there was any benefit to weighing cases I would do it.

 

[rayjay]

This is why I bought preprepped brass from Hoehn when I got my 6ppc. Already weight matched, expanded and neck turned. Load em and shoot em.

 

[olympian]

It depends on the case and the gun. A grain or two in a 300 Ultra Mag is not going to make much difference in most guns. If it is a high quality BR gun, sort by 0.5gr or so. I sort by 1% of an empty prepped case for most non-BR guns.....law of deminishing return

 

[Rtheurer]

Good question but how do you know when weighing cases that where the weight differential is will effect case volume? Point is you can't so to make this type of activity worthwhile you would have to check each cases volume individually.

Slow P.R.

I have a Question? If you size your cases and turn the necks and uniform your primer pockets, and you are getting 3 Grains of weight E.S. Then where is the diffrence in weight comming from. The outside of the case is the same from one case to another because I have sized them all to the same outside dimension. I was under the impresion that if you have the exact same outside dimensions then the heavy cases would indeed be a little smaller in the boiler room of the cases. Is this an incorrect assumtion? Physical Science tells me that it would indeed be smaller internal volume, Maybee My 8th grade science is not enough to understand the complexities of reloading. ; )
When I started shooting the 6.5X284 the only commercial brass available,pre Lapua/Norma)was Hornady Brass and of course Winchester. That Brass sucked as far as weight E.S. is concerned and I didnt figure it out till about a year and half later. Once I weight sorted it all my myserious flyiers went away and my vertical spread at 1000 dramaticly decreased. Thats all I have to work with is actuall feild testing so help me if Im incorrect. Is it in my head?
Im going to feel silly if I have been weight sorting all this brass for nothing.

Please help.

RussT

 

[CatShooter]

I think there is an assumption that cases are made the same, so if there is a variation in case weight, it MUST represent a difference in case volume, because it would represent a variation in wall,or other part) thickness.

Some times it does... I have a high quality 308 match rifle, that typically shoot in the 3's. I bought a new batch of Fed GM match brass and the rifle became a 1.3" rifle.

After much sweating, I discovered that the new "match" cases were weighing between 155 and 176 grains, and I don't mean that just a few pieces were out and the rest were clustered around some magical number... the cases were all over the place.
The rifle that had previously been a ~0.3" rifle, now was shooting all over the place.

So I picked 20 pieces at 155-156, and 20 pieces at 175-176, and loaded them with weighed charges.

100 fps difference with an ES of 12 between the two batches.

Simple math makes that 5 fps per grain of case weight, but ES for most 308 loads with selected and weighed cases is ~10 to ~20 fps...
... and if you take a single case and load it 20 times at the range, there will still be variations in ES and SD of 10 to 20 fps.

So two or three grains of weight get lost in the statistical "noise".

So at some point, it becomes a worthless effort. Some guys weigh cases to 0.1 gr. That means that in order to get 100 "useful cases", you will need to buy ~400 to ~1,000 cases - maybe more.

The other problem is that the variation in weight could also represent a variation in the extractor groove.

Weighing them with water isn't accurate because even if they have identical "volume" under pressure in a chamber, they may NOT have the same volume sitting on your bench, because of variations in brass hardness and "spring back".

I don't bother weighing quality cases like Lapua. I do sort domestic brass by weight, IF the accuracy level of the rifle warrants it... but even then, I'll cull the extremes, and keep the middle 80%-90% cluster.

I don't buy Fed GM brass anymore! :,


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[chuckw2]

I weighed 100 Laupa 6.5 x 284 cases one time....I had to stop because I was afraid I was going to shoot myself....I just do not think it is time well spent...

 

[CatShooter]

I weighed 100 Laupa 6.5 x 284 cases one time....I had to stop because I was afraid I was going to shoot myself....I just do not think it is time well spent...

HA!...

A while back I bought a Remington Sendero-II SS-SF in 264 for feral dogs.

the first preliminary loads,w/Winchester brass) looked so good, that I decided to "sort the cases".

I weighed 30 of them, and the total "high to low" variation was 1.2 grains,!!).

Now that's embarrassing... At that point, I quit!


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[SlowpokeRodriguez]

Good question but how do you know when weighing cases that where the weight differential is will effect case volume? Point is you can't so to make this type of activity worthwhile you would have to check each cases volume individually.

Slow P.R.

I have a Question? If you size your cases and turn the necks and uniform your primer pockets, and you are getting 3 Grains of weight E.S. Then where is the diffrence in weight comming from. The outside of the case is the same from one case to another because I have sized them all to the same outside dimension. I was under the impresion that if you have the exact same outside dimensions then the heavy cases would indeed be a little smaller in the boiler room of the cases. Is this an incorrect assumtion? Physical Science tells me that it would indeed be smaller internal volume, Maybee My 8th grade science is not enough to understand the complexities of reloading. ; )
When I started shooting the 6.5X284 the only commercial brass available,pre Lapua/Norma)was Hornady Brass and of course Winchester. That Brass sucked as far as weight E.S. is concerned and I didnt figure it out till about a year and half later. Once I weight sorted it all my myserious flyiers went away and my vertical spread at 1000 dramaticly decreased. Thats all I have to work with is actuall feild testing so help me if Im incorrect. Is it in my head?
Im going to feel silly if I have been weight sorting all this brass for nothing.

Please help.

RussT

Anything you do with respect to weighing the entire case is meaningless with respect to the interior volume of the case. This means that you are making the assumption that by having 2 cases of the exact same weight that they have the identical internal volume. This is not a valid or logical assumption however; those two cases may just by happenstance have the same volume. Now we know that the internal volume of the case is what determines powder capacity and if the cases are different volumetrically, they will develop different pressure curves which will translate into different velocities. This will include among other things possible POI changes as well in addition when shooting at distances that are long enough the vertical dispersion caused by the different muzzle velocities will be very noticeable.


If you in fact want to check the interior volume of your cases, then start with clean cases and fill each one with a powder that flows readily such as 748 to the top of the case and then weigh the charge. This takes more time plus you have to use water but fill each case with water,eye dropper or bulb syringe) and put a few drops of surfactant in the water,i.e. 1 gallon jug) to break the surface tension to ensure no voids,tiny bubbles) on the inside of the case. If you add surfactant or dishwashing soap, make sure you rinse them well when finished. It is as pointed out above a tedious procedure that has questionable results. Do I do it for my competition rifles -- no FWIW..

 

[Rtheurer]

Slowpoke

Im not sure I got a satisfactory answer. Please bear with me if you will.

If I size my cases on the outside to include the body and neck and then stick them on the digital scale, if I have a Extreme Spread of lets say 4 grains where is the diffrence comming from? I still cant fathom that it is anywhere but the internal volume of case do to the wall thickness or base thickness. Minus a little bit for spring back of course but what gives? I must not be getting something here. Now Catshooter's thought on the extractor groove giving a little bit of E.S. makes sense to me., as you can tell im a little slow)
Im shooting at a National level and do not want to take ANY chances. Just as Lynn mentioned it is not worth it in my book I have too much invested at this point. Sorry if I did not mention results at 1000 yards versus anything under 600 yards where Im thinking you can get away with alot more with no ill affect.
ChuckW2:
Man I have been there buddy. I have a bunch of Lapua 6.5X284 brass and some of it was not very good. I thought why am i spending the extra money on this Lapua brass? But I still weigh it and sort it into batches. Im scared im going to have the heaviest peice right next to the lightest peice in my loading block,, I have no Luck and except it). then I pop one out the top at 12:00 and the next one is out the bottom at 6:00 and I broke two perfect shots for nothing! You CAN NOT loose two points at the nationals for elevation and expect to do well!!!
Even with Norma or Lapua brass for 1000 yard shooting I weigh them out and put them in my loading block from light to heavy and load them that way when I shoot. That way I have one round no more than .1 from the last shot. I might have a four grain diffrence from number 1 too number 200 but I did not throw away any cases and I have a great mental mind set that I did the best I could with what i have.
Under 600 yards all the above may not matter one little bit?

Slow Poke Help me out here, if you would be so kind sir, I must not be seeing the big picture?

Thank you

RussT

 

[Varminator]

I really don't have the experience or the "experience" to even post on this thread, but.. after all is said and done, extreme case preparation, bullet weighing, case volume, neck tension, powder weight to the nearest hundredth of a grain,yada yada); Shouldn't we just cull our rounds by where they shoot?

And if primers can change how a load behaves then how do we know that the primers are consistent?
><MM>

 

[6hangingC]

I am a newby to this precision long range shooting, and am in the process of buildilng my first long range rifle,6.5x47 Lapua). I have learned a great deal from all you experienced shooters, and think this site is excellant. I certainly have nothing to offer this thread, but I have a couple of questions...These may be stupid questions, being the newby that I am, but here goes anyway.....

#1 Has anyone, after sorting brass by weight, checked the volume of the brass to see if the differences in volume was consistent with the differences is weight.
#2 After you have sorted your brass, and lets say you end up with 3 differnt groups, each within your acceptable allowances. What do you do with these 3 different groups?? Do you load them the same and try to compensate for the differndce in trajectory., or do you load them differnt??

 

[Ackman]

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#1 Has anyone, after sorting brass by weight, checked the volume of the brass to see if the differences in volume was consistent with the differences is weight.

Yes. It's very difficult if not impossible to get consistent accurate, repeatable readings with even the most fine grained powder. I used water volume. This with 2 different brands of .223 cases, 40 or 50 were weighed to find the heaviest and lightest, along with a bunch in the middle. Weighing brass as it comes from the factory is meaningless. They need to have the same length and to be precise, the same neck thickness. These chosen cases were fired, sized, trimmed to identical length, and weighed. Then they were neckturned and re-weighed.....neckturning didn't change the outcome. Water volume was very carefully checked and rechecked. The results.....water volume was unpredictable. With one headstamp the heaviest case had the most water volume......with #2 headstamp, the heaviest case had the second most volume. There was no correlation between caseweight and volume. Interestingly, one headstamp varied considerably more in weight from heaviest to lightest compared to the other, but case volume difference from most-to-least was about 1/7th as much.

Weight can be anywhere in the case including the rim and extractor groove. Sorting by caseweight accomplishes nothing.

 

[CatShooter]

".... Sorting by case weight accomplishes nothing.

With the exception of the one batch of Fed GM Match cases that varied by 21 grains, I agree - I have never been able to discern and improvement by weighing cases.


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[6hangingC]

Thanks for the imput guys. All your informations is very helpful.
From what I seem to understand from all this is that: case weight and case volume have no real common denominator, so if a person is to do any sorting of brass it should be done by measuring volume and not worry so much about case weight.
BUT....,here comes maybe another stupid question).. If I precisely weigh each powder charge, how much of an effect does a little difference in case weight or case capacity actuallly have in accuracy?? And if in fact they do have an effect on accuracy, how do they affect it??

 

[rasp65]

I have weighed and sorted cases by water capacity before. My question is how do you plug the flash hole? I used the same spent primer for each case, it was tedious to say the least.

 

[Ackman]

Using the same spent primer for each case??! You're kidding.........