case weights vs volumes

[Tesoro]

I have been working a load for my new 20 practical and have been getting unacceptable sd for the level of uniformity I put into my loads. yeah I know the variables and one is off and i'll figure it out. I thought that the culprit was case volume variation as I had not weighed/batched my cases as they were all unfired 2016 LC 223. So I took the cases, weighed all 25 of them and there was a spread of 94.4 to 96.8 grains. So I said gotya and then did water weighing. i didnt do them all but picked out the 12 extreme ones. Surprisingly what I found was the volumes were pretty much all the same 30.5 to 30.9 grains.

I had done this previously with some nosler match brass and the volume spread was more than with this LC brass.

Anyhow just interesting that the weight variances didnt correspond to volume variances - at least in this batch.

Water weighing is a bit of a pita. Would like to figure out something else to pour in there such as mini bird shot like in 22lr bird shot loads. anyone know of a good medium to use?

 

[Deleted member 46119]

Anneal the neck and shoulder

 

[Mikecr]

I've measured mismatches both directions, and so I credit only H20 capacity measurement.
All anyone need do to understand this is consider two cases matching in weight but one of them FL sized with the other NS'd only. They still weigh the same but their capacities and loaded densities are changed by the sizing and spring back actions.
Given this, there is as much potential for removing the very best of your cases, with brass weight culling, as removing the worst.

It's an example where understanding is far more important than action.
It's also an example of how taking shortcuts (as weighing brass is easier) can hurt you.

 

[DocDoc]

Any ball powder would give a comparative volume measurement and not involve the hassle of water.

 

[Tesoro]

Any ball powder would give a comparative volume measurement and not involve the hassle of water.

duh! thanks for the suggestion! the solution was staring me right in the face. now i can give my wifes cajun injection syringe back to her...

 

[Deleted member 46119]

I've measured mismatches both directions, and so I credit only H20 capacity measurement.
All anyone need do to understand this is consider two cases matching in weight but one of them FL sized with the other NS'd only. They still weigh the same but their capacities and loaded densities are changed by the sizing and spring back actions.
Given this, there is as much potential for removing the very best of your cases, with brass weight culling, as removing the worst.

It's an example where understanding is far more important than action.
It's also an example of how taking shortcuts (as weighing brass is easier) can hurt you.

I'm with @Mikecr that H2O or "ball powder" volume measurement is only and "indicator". How the brass is sized and how it expands in the chamber are very important as well.

There is one important thing to remember through this. Mass = Volume. A certain weight of brass (mass) is going to have a certain volume. Physics is physics and you can't argue with it. A chamber is going to have a volume. Subtract the volume of the brass from the volume of the chamber and you get a measurement that is useless. Well not really. It is the amount of room for the pressure to expand into. Most of this volume is inside the case and the case expands during the firing process to use this space.

We refer to "fire formed" cases a lot. In fire formed brass, the mass of the brass has been expanded like a balloon to match the inside of the chamber. This is not a perfect thing and that's why two pieces of brass with the same weight/mass can measure different volumes.

So regardless, weighing brass and measuring H2O are only "indicators".

The are useful indicators for many. Me included.

If all your brass is very close in weight, and all your brass is very closely formed to the chamber, it reduces variations. Add consistent annealing. Consistent primers. Consistent neck gripping and release pressure. Consistent bullet shape, weight and seating.

You up your consistency. That is all it does. Increasing consistency is what it's about for accuracy.

Clear as mud right.

 

[Deleted member 46119]

I forgot something that I think @Mikecr and I disagreed on before but we may be closer now.

The "shape" of the inside of the case like how thick the base is or how thick the walls are.

Previously I believed that this did not have any effect. I was right and wrong at the same time. I was right that it does not effect volume if the outside of the case is well fire formed. Where I was wrong is that the share and where brass is thick or thin effects how the gasses expand. Quality brass will be more consistent on it's internal shapes like wall thickness and base thickness. So it will "shoot" better. Lapua and Norma are more dimensionaly consistent.

The bummer is that to measure this AFAIK you have to destroy the case.

 

[Tesoro]

Mass = Volume?

I spoke to one of the guys at Redding yesterday ref a die issue. We got into a case discussion briefly and neck turning. He said he gauges the quality of an individual new case by measuring the neck wall as any large variation will carry on into the case body wall. Any variation of 1.5 tho and over gets tossed. And he dosent bother turning the necks if within spec.

I laid out 50 new LC 223 trimmed brass yesterday for a test to this. Neck thickness was .0115 to .0125 consistently - none were tossed.

Of the 50 about 70% weighed in the same grain range of ie 93.0-93.9...the rest were either one grain heavier or lighter...ie 94.0-94.9 and 92.0 to 92.9 grains. I took 4 of each 1 grain over and 1 grain under the 93 range that weighed the same or within a grain. I then did a vol test with ball powder. The results showed that the volumes were pretty much the same with a 2 grain spread in weights.

And then I realized this exercise was pretty much a waste of time when I thought about how casings are made! The brass is drawn over mandrels in stages to stretch it and form it punch it etc and somehow any excess brass must form/expand on the outside of the case and not the inside. This is backed up by neck turning the outside of the neck to even the thickness vs reaming the inside which dosent do it.

So is the moral of the story to sort NEW brass by checking neck consistency like the Redding guy said!? Ha.. And only check volumes for certain case batches for comparison of power charges and published load data with case vol notations.

Its raining windy and cant shoot so I am obviously in the overthinking mode.

 

[Pdvdh]

I've weighed 3,700 .223 casings from approximately 15-20 different manufacturers.

I learned a lot by the end of that effort. I recorded the weight of each case. Calculated the ES, SD, and Avg weight for each brand of casing.

The lightest brand weighed around 89gr Avg. The heaviest brand weighed around 107gr Avg.

Weighing brass provides a lot of useful information about case capacity. Whether or not the information is useful for you and your uses, is up to you and you alone.

I have to reduce a charge of Varget by 0.4gr to get comparable MV from a case weighing ~105gr, compared to a case weighing ~92gr.

If I shoot the same powder charge in the heavier case as I load in the 92gr case, I'll get ~175fps additional MV, along with substantially higher chamber pressures.

I now keep an 11"x17" printout [Excel Spreadsheet] of all the .223 casing weights and statistics according to brand, from lowest Avg weight to highest Avg weight on the back of a reloading wall cabinet door above my reloading bench as a handy reference.

If I'm going after maximum uniformity, I'll select a brand with the better uniformity.

I've culled 10-15% of cases in order to reduce the variance in case capacity. So there's maybe 400 cases bagged separately as seconds, which would only be used for plinking. Or more likely, will never be used by me.

 

[Tesoro]

I guess thats what one does in Alaska in the winter when snowed in your cabin! but you are only half way there..now to do volume comparisons!!! That should only take another 60 hours.

I think the bottom line is to check the volume on a new batch of cases to see if you are within the norms for your loads. And then sort by weight and check neck thicknesses if going for accuracy.

The other day I was loading up some 223/55gr noslers and checked nosler's loads for h335. I happened to notice that their case vol was 27.5g h20 and thought that weird as most common 223 run around 30g. Maybe they were using heavier walled norma/nosler? either way the max load would be diff for a 30g vol case than their data.

 

[Pdvdh]

I meant to include that I also outside neck turned all casings, primer pocket uniformed, and deburred firing pin flash holes on all casings, except some of the culls. Annealed all case necks. And of course trimmed and dechamferred case necks.

By the time I was through, I'd learned quite a bit about the relative quality of the different brands of .223 brass.

Outside neck turning reveals the consistency of case neck thickness. I tested concentricity on almost all case necks. Learned that the thicker side of a case neck will cant a seated bullet toward the thinner side of the case neck.

Also learned that outside neck turning will reduce a lot of the bullet runout from a case neck thin on one side and thick on the other, but not all of it. And following the firing of that case in the rifle, the bullet runout following the firing, resizing and reloading of the outside neck-turned cases was almost always improved further.

Lastly, after all these case preparation and load development steps, I learned that crimping my loaded cartridges with the Lee Factory Crimp Die improved precision of my reloads as much, if not more, as all the other OCD-prompted steps combined.

 

[Pdvdh]

Yes, it was a winter time hobby...

 

[Tesoro]

All interesting input. BUT the one thing I have learned is that over messing with neck turning can degrade accuracy over factory necks that arent much out of whack. Thus the crimp as you stated, which in its own way, can re-create the equiv. of more even neck pressure in its own way.

I am not sure if controlling runout is more important than neck grab when seating close to the lands. I am talking about minimal runout like up to 2 thou vs neck grab.

Once I decided to apply a little bit of imperial wax to my bullets before seating into very concentric necks. The groups opened up considerably and so did my velocity spreads. Normally I dry seat my small bullets and my best group has been .169 with 20 cal.

When I upgraded to a 21C neck turner I started playing with it as was very cool and so precise. The resulting necks were turned to 'all shiny' being perfect beautiful and concentic less than or = .0005 but they didnt group as well as as factory ones within a thou tolerance.

I learned that every time you mess with your necks you heat cool and move that thin piece of brass thus making the neck grabbing pressure uneven from case to case.

I am no longer a believer in the common thinking that if you neck turn brass you should do at least x% coverage. All I do anymore is slightly bump the high spots.

This is akin to some shooters who like to pour caustic ammonia products down their barrels to get rid of that lovely copper buildup that has smoothed out their barrels!

 

[Pdvdh]

Outside neck turning reduced neck and seated bullet run out. I don't clean up the entire neck exterior. Around 50-65%, unless there's an abundance of neck wall thickness.

I HBN coat all bullets.

I lube the case neck interiors with Hornady Unique resizing wax.

These steps all reduce case neck to bullet friction and grip/hold, and reduce the variance in case neck bullet grip between loaded rounds, IMO.

However my 223 is an AR15. Mag lengths prevent seating bullets near the lands, and the slapping of the rounds into the chamber requires that the bullets be gripped reasonably securely by the case necks. So I purchased a LEE Factory Crimp Die and precision improved about 40%. Now my loads shoot better on paper, and are more reliable in function thru my semi-auto.

It's rare to find examples where the LEE crimp die harms precision. I spent hours researching this. By and large, the folks pooh-poohing the crimping had never even tried it. Armchair experts. If the benchrest competitors didn't crimp, then it couldn't possibly be good. In fact some considered it pure evil. And they'd never ever tried it.

Well how many of our LRH rifles are constructed for benchrest competition? And how is that argument pertinent / relevant, if my precision improves in my hunting rifles after crimping my best developed loads?