Sorting brass by weight

[gunlaker]

Years ago I took a batch of fireformed Starline cases and sorted them by weight and then measured the volume using roughly the same technique. It would have been 40 or 50 cases. I plotted weight vs. volume and the graph made it pretty clear that there was no meaningful correlation.

I think that the brass made for these types of rifles is not made with anything like the consistency of true match brass, like Lapua .308 brass for instance. It would be interesting to see if there was anything at all that could be done to these cases that would significantly improve velocity variance.

Chris.

[TexasMac]

You guys have me questioning my measuring technique. It turns out rightly so. It's very hard to determine when the water level is the same when filling the case, even using light reflection as an indicator. So I redid the measurements and determined that I am unable to measure a difference in the water weight between the three cases due to inaccuracy in determining when the cases are full to the same level and the weight of the drops of water being dispensed by the syringe. Based on Clarence's comment about the density of brass vs. water I checked and brass density is listed as 8.73gm/cm3.

Therefore, assuming all external dimensions are equal, the difference in the lightest to heaviest case is 2.7gr, which should equate to a water volume weight difference of only 0.31gr. I just compared a case full of powder (~89gr) vs. a case full of water (~80gr). So we are talking about a difference of only 0.34grs in the powder weight. Assuming 0.020" of compression per grain of powder, 0.33grs of powder equates to a compression change of only 0.007".

So marking the cases was a waste of time. But it was worth the time to measure the cases since I sure learned something in the process. Thanks guys for questioning the water volume measurement results.

Wayne

[gunlaker]

Wayne I think that the water technique makes for a pretty large uncertainty in the measured volume. I also tried measuring the same case multiple times to get a handle on the magnitude of the uncertainty.

A very fine solid like flour might be more consistent, or maybe a fluid with less surface tension.

Chris.

[mdeland]

I'm wondering if there is a correlation to weight/capacity and SD. I'm guessing with the relative inefficiency of BP and the much lower pressure, if any advantage at all of a grain or two (let alone a few tenths) of case weight can be measured at target.
Is it not easier to get lower SDs with BP than with smokeless? Also BP seems to respond better to volumetric regulation than does smokeless so I'm thinking that comparison to the smokeless match brass is apples to oranges.
The efficiency of the burn I think does play a part because I have read that BP typically is only about 55 percent efficient in turning solid to gas where as smokeless converts a much larger percentage of the original mass.
Being the case that BP appears to respond better to volume/ compression than weight I would think and SD comparison to case weight might be a better comparative measure.

[desert deuce]

Time for this Shelter in Place stuff to end.

Or, Next folks will be paper patching primers.

[bruce m]

as long as they don't anneal primers.
bruce.

[gunlaker]

Time for this Shelter in Place stuff to end.

Or, Next folks will be paper patching primers.

Just don't wet patch them .

Several years ago I spent a lot of time trying to assemble a perfect batch of brass by sorting by weight, neck and rim thickness, and it didn't seem to make any difference over just opening a bag of brass and using them as they were. Maybe two years ago I learned that just dropping charges out of my MVA powder measure also works as well as weighing them, same with bullets, at least out to 300 yards. Actually my very best practice targets have all been shot that way. I don't think that there is a lot for me to be gained spending more time experimenting with loading techniques.

If I could only find a way to be as carefree about the wind and mirage then I'd really be onto something.

Chris.

[Kurt]

Time for this Shelter in Place stuff to end.

Or, Next folks will be paper patching primers.

Heck Zack they already do when they put paper in the primer pocket and seat the primer

Wayne use table salt to measure the volume. If you look at the salt crystals through a strong magnifying glass they are square and very uniform fill the case and street it off flush.
Water unless you set the case on the scale and re zero it then fill the case with waters till it's level then take the reading and then dump it.
Weighing the water dumped from the case into the pan to weigh will give a bunch of variances from more or less staying stuck to the case.

Neck tension and wad stack will give you a better low vertical down range using black powder. !/2 to 1 grain more of less does not do much for velocity but it will effect the compression playing with burn rates.

For HP bench rest with smokeless I would worry about the inside volume.

[SSShooter]

Am surprised by the volume difference at those relatively small weight differences. I usual sort brass into 3gr lots. Based on your measurements think I'll tighten that to 2gr lots. Thanks for the effort, Wayne.

A long time ago, before good brass like Lapua or Norma was available, I had (still have) a tool that fits on my RCBS electric prep tool that would shave all the brass tailings from the powder side of the primer hole. Win & R-P and LC cases were all made by 'poking' the primer hole and plenty of 'flash' on the inside. Have never bother to look inside our cases, but one could always do the same and perhaps get a more consistent ignition/burn. If you do, let us know how it works out.

[SSShooter]

Ha, ha........ should have read page 2 before replying. Back to a 3gr sort.

[TexasMac]

Am surprised by the volume difference at those relatively small weight differences. I usual sort brass into 3gr lots. Based on your measurements think I'll tighten that to 2gr lots. Thanks for the effort, Wayne.

A long time ago, before good brass like Lapua or Norma was available, I had (still have) a tool that fits on my RCBS electric prep tool that would shave all the brass tailings from the powder side of the primer hole. Win & R-P and LC cases were all made by 'poking' the primer hole and plenty of 'flash' on the inside. Have never bother to look inside our cases, but one could always do the same and perhaps get a more consistent ignition/burn. If you do, let us know how it works out.

Glenn,

When preparing new cases I always deburr the inside of the primer flash hole after expanding the case neck & trimming all the brass to the same length to ensure deburring tool cuts burrs to the same depth. I use a Lyman Case Prep Express (Lyman's version of the RCBS electric prep tool) with a flash hole deburring tool so the process is fast. Does it help. I have no idea but it increases my confidence that the brass is the best I can make it. Once done it never needs to be repeated.

Wayne

[bruce m]

I have never had any lapua brass with better max to min weights than waynes batch here has.
I have used a fair bit of it shooting fclass, and feel that while it is good, it is not as good as urban legend would have us believe.
rws brass is if anything better for weight, and way better for consistency of metallurgy.
nowadays I by say 200 cases and divide them by weight into 4 lots of 50.
the 2 middle lots have the least variation, and are kept for long range or scheutzen.
I must admit I cannot tell the difference between the better lots and the less good lots.
I anneal my black powder brass a little more than smokeless cases, so it is a little softer offering obturation at lower pressures.
I do not size cases, so would test capacity after about 3 or 4 shots in the hope that exterior dimensions were as consistent as possible.
I have never found cases of any brand that cannot benefit from internal deburring of flash holes, as well as uniforming their diameter.
wayne is chasing a worthy cause here, but it is what I call a 1 percenter.
but all those 1%s add up, both on the range and between the ears.
of course the pursuit of small things can be negated if one big thing is overlooked.
bruce.

[SSShooter]

I use a Lyman Case Prep Express (Lyman's version of the RCBS electric prep tool) with a flash hole deburring tool so the process is fast.
Wayne

Do you have 40 & 45 cal pilots for your deburring tool? If so, where did you find? Would be much simpler to purchase than to make.
Have 600 new cases to deburr and should get started.
Thanks.

[CaptnJack]

I have some older Bertram Brass from about 20 years ago in 45 basic 100 rounds and some newer 45-120 Norma brass. Just looking at the brass you can tell the Bertram is heaver. I cut both down to fit my 45-110 and decided to weigh a few. The Bertram is 12-15gr. heaver than the Norma brass right off the bat.

[TexasMac]

I use a Lyman Case Prep Express (Lyman's version of the RCBS electric prep tool) with a flash hole deburring tool so the process is fast.
Wayne

Do you have 40 & 45 cal pilots for your deburring tool? If so, where did you find? Would be much simpler to purchase than to make.
Have 600 new cases to deburr and should get started.
Thanks.

Glenn,

I use a Lyman universal flash hole deburring tool which can be used in the electric case prep unit. It has a sliding tapered pilot that will fit the mouth of any case (.22 to .45 cal) and is adjustable for depth. The key with using it is the case mouths must be uniform and the cases trimmed to length prior to deburring to ensure the tool cuts to the same depth. Here’s what the tool looks like with the detachable handle: https://www.brownells.com/reloading/cas ... 99268.aspx

For deburring tools that use specific pilots for each caliber such as the RCBS or Sinclair, pilots are available from Brownells, RCBS and possibly others. Here’s a link to the Brownell/Sinclair pilots: https://www.brownells.com/reloading/cas ... 33071.aspx; and the RCBS pilots: https://www.brownells.com/reloading/cas ... 03870.aspx

Wayne