Weight sorting cases... opinions solicited

[DougMH]

I have another theory for getting a lower standard deviation (SD) on muzzle velocity (MV).

A lot of people weight sort cases. I think that’s a waste of time because of inherent varying densities in the brass, especially in the head stamp area. What you really need to do is volume sort cases (which is what case weight sorters think they’re doing).

My method would plug the primer hole, place the empty, unprimmed but otherwise fully prepared case on a scale, tare to zero and fill it with a fluid (TBD but probably paint thinner because it’s less dense than water, has less capillary action than water and would evaporate quickly after being blown out). By taring the plugged case to zero (0), the reading would be the weight of just the liquid, and hence the volume. Filling the case would be much like measuring powder. You could use an eye dropper for the initial squirt, then trickle liquid until it came to the top without spilling over.

And please, no environmental whacko comments about the inherent dangers of using paint thinner. Life is full of risks.

 

[mc223]

OK, You check it out and keep us posted. I gotta go wash and wax the shooting cart.

 

[Jayman_10x]

I have another theory for getting a lower standard deviation (SD) on muzzle velocity (MV).

A lot of people weight sort cases. I think that’s a waste of time because of inherent varying densities in the brass, especially in the head stamp area. What you really need to do is volume sort cases (which is what case weight sorters think they’re doing).

My method would plug the primer hole, place the empty, unprimmed but otherwise fully prepared case on a scale, tare to zero and fill it with a fluid (TBD but probably paint thinner because it’s less dense than water, has less capillary action than water and would evaporate quickly after being blown out). By taring the plugged case to zero (0), the reading would be the weight of just the liquid, and hence the volume. Filling the case would be much like measuring powder. You could use an eye dropper for the initial squirt, then trickle liquid until it came to the top without spilling over.

And please, no environmental whacko comments about the inherent dangers of using paint thinner. Life is full of risks.

In terms of determining case volume, I think you're on to something. I used to weight sort brass, but after a few tests just haven't found it to be worth while. Instead I focus on ensuring concentricity of the case, bullet round out, neck tension, correct case or neck sizing technique, and optimal overall length.

Now, if you're a 1,000 yard shooter everything comes into play, so there you're method would likely be beneficial. However, up to 600 yards, I have not observed any benefit to weight sorting brass. Which suggests volume sorting may not be beneficial either. Just my $0.02.

Jason

 

[artbosco]

I think that’s a waste of time ...

That's certainly a true statement especially if you're using LAPUA brass. However, if you're using something else, there can be large variations. If you find that to be true of what you're using, sort before doing anything to the brass or sort after everything has been done.

 

[DougMH]

... neck tension...

Jason

It so happens I've also developed what I think is a new and better way of measuring neck tension. I'm working on it with John Whidden of Whidden Gun Works. Until we do some testing, I can't say much more about it because it may develop into a product. I will keep the forum posted with any information I can release.

I certainly wouldn't underestimate even small variations in case volume though.

I have an old saying, "I only <put anything here> for the fun of it, but it's no fun if I don't win!"

Therefore, regardless of distance, it's all important to me... do they have an Accuracy Anonymous chapter around here? I'm sure I could use a 12 step program.

 

[memilanuk]

When you come up with something that is workable for 500-1000 case lots, let me know.

As it currently sits, sorting by volume for any meaningful quantity of cases is a quick way to make you want to gouge your eyes out with a cleaning rod...

FWIW... the limited runs of sorting by volume vs. weight that I've done showed that there is *some* relation between the two. It's not a simple one-to-one relationship, and as mentioned not all the change in volume can be explained by changes in weight - plus/minus tolerances elsewhere, such as the case head, influence this. But as far as a cheap/easy way to quickly separate the really heavy from the really light cases - the ones most likely to have some meaningful volume variation - simply sorting by weight is hard to beat.

 

[DougMH]

When you come up with something that is workable for 500-1000 case lots, let me know.

As it currently sits, sorting by volume for any meaningful quantity of cases is a quick way to make you want to gouge your eyes out with a cleaning rod...

I hear ya!!!!!! Read my previous post. I really do need help.

 

[Erik Cortina]

Well, shouldn't you fireform the brass to your chamber first to ensure that all the brass is of identical size, at which point you would need to clean the brass thoroughly to make sure no carbon deposits are left inside that would affect volume. Also, whatever method you use to clean brass, make sure it doesn't put any dings on the brass or that they rub or bang against each other at all or case volume might be compromised.

One more thing, if you say even small case volume variations matter, then after you fireform the brass, how do you know they all had the same spring back?

 

[DougMH]

Well, shouldn't you fireform the brass to your chamber first to ensure that all the brass is of identical size, at which point you would need to clean the brass thoroughly to make sure no carbon deposits are left inside that would affect volume. Also, whatever method you use to clean brass, make sure it doesn't put any dings on the brass or that they rub or bang against each other at all or case volume might be compromised.

One more thing, if you say even small case volume variations matter, then after you fireform the brass, how do you know they all had the same spring back?

I would say eiter all fire-formed and neck sized or all full-length resized and not a mix even if the volume was the same. My reasoning is that if you have fire-formed and full-length with the same volume, the full-length is going to expand in the chamber on detonation where the fire-formed will not... at least not as much.

I agree completely that the brass must be cleaned ultra-sonically not tumbled with possible corn dust/chemical still in side. I want to look into the case mouth and see some shine inside whether new or fired.

Also, I anneal EVERY firing. I've read a lot about it and it can only help with case life.

I'll try to put a video together at some point. Anyone is welcome to take what they like from it and discard what they don't.

I have a pretty decent video facility on this PC (Pinnacle Studio Ultimate and a Canon AVCHD camcorder (no tape)).

 

[mikecr]

I've done H20 capacity checks for many years, and have noticed inconsistent correlation between case weight and actual volume. My approach:
1. Fully prep, and fire form new brass twice
2. Stand each case (on a plastic golf tee pressed into flash hole) on my scale & zero
3. Eye drop water with just a touch of alcohol mixed, to case mouth
4. Tissue corner away meniscus, for flat to mouth weight reading
5. Enter value in QuickLoad

Do not size cases prior to capacity checks, if for comparison. This would serve only to increase variance. But if you will be full length sizing, then do so with a few & capacity check for QL.

 

[22XC Guy]

Here's another good thread of information...

http://www.accurateshooter.com/forum/index.php/topic,3761214.0.html

Steve

 

[DougMH]

I've done H20 capacity checks for many years, and have noticed inconsistent correlation between case weight and actual volume. My approach:
1. Fully prep, and fire form new brass twice
2. Stand each case (on a plastic golf tee pressed into flash hole) on my scale & zero
3. Eye drop water with just a touch of alcohol mixed, to case mouth
4. Tissue corner away meniscus, for flat to mouth weight reading
5. Enter value in QuickLoad

Do not size cases prior to capacity checks, if for comparison. This would serve only to increase variance. But if you will be full length sizing, then do so with a few & capacity check for QL.

Sorry, not following this at all. You're saying do the volume measurement, then size the brass? In addition to a whole lot of other things, when I put a round in my rifle at a match, I want the amount of powder in every one of them to be the same and I want the internal volume of every one of them to be the same. I don't see how that can be attained by volume sorting, then sizing. Maybe I'm misinterpreting what you said.

 

[mikecr]

You're saying do the volume measurement, then size the brass?

Cases are never more consistent than pulled from a smoking chamber.
So when comparing cases, this is the point to do so.

In addition to a whole lot of other things, when I put a round in my rifle at a match, I want the amount of powder in every one of them to be the same and I want the internal volume of every one of them to be the same.

If that's REALLY what you want, you'll size your brass as little as possible.
With every energy added to cartridge brass, you add dimensional variance.

I think you're going to learn a great deal with capacity checks.

 

[DougMH]

Cases are never more consistent than pulled from a smoking chamber.
So when comparing cases, this is the point to do so.

Sorry, I can't buy it. You put water (or other fluid) in one case still filled with powder residue. When you dump the water, how much of your volume comes out with the fluid (maybe more for one case than the other). Plus you're still going to have to neck size the brass at a minimum, that will alter the volume as well.

If you anneal every time or maybe every other time, you're not going to over work your brass for several reloadings, especially if you neck size only. Clearly the point to take the volume measurement is with a completely clean and prepared case sans primer, powder and bullet.

 

[mikecr]

With regard to H20 capacity checks, powder residue amounts to nothing, and affects nothing. It adds no weight & you'll tumble & dry afterwards.
Annealing, or overworking brass, has nothing to do with capacity checks.

Typically capacity checks are done to identify variance and cull it out. This follows other culling performed, like thickness variance measurements.
So no matter what you do with your brass from there, you know it atleast initially matches.

Now if your objective is to match capacity in new or FL sized cases, then you should precondition yourself for results no better than empty case weight.
If you use custom dies & size minimally & really seek matched capacity in loaded rounds, then I salute your endeavor. You can do it.
But not till the brass is fully fireformed, atleast.
I size my brass so little that capacity variance from it holds within my original culling tolerance.

 

[DougMH]

With regard to H20 capacity checks, powder residue amounts to nothing, and affects nothing.

Clearly you don't clean with a sonic cleaner or you'd know the folly of that statement.

 

[Jayman_10x]

A lot of input here. I would say for the time concious of us, just buy Lapus brass (if possible) and go shoot up the X-ring.

Problem solved.

-Jason

 

[coyoteklr]

As it currently sits, sorting by volume for any meaningful quantity of cases is a quick way to make you want to gouge your eyes out with a cleaning rod...

+1+1+1 LMAO

 

[4xforfun]

I think you guys are wasting your time.

If you have fire formed casees, all full length sized so as to have all of the cases EXACTLY the same size and LENGTH (outside measurments)...all have been cleaned ect...the heavier case is going to have less volume....period!!! If a piece of brass is heavier, that means it has more brass...and that brass has to be somewhere...and that somwhere is INSIDE THE CASE.....so yah...that case will hold less water. But you already knew that, because you just weighed the case.

Why waste your time with the volume test? It makes no sence to me.

 

[DougMH]

Oh! I love to shoot in matches against guys who "... don't waste their time..."