Rifle Brass Sorting Experiment - Part One

[ammolytics]

Hey everyone!

I published the first part of an ongoing experiment which explores the relationship between the weight and volume of rifle brass.

https://blog.ammolytics.com/2020-01-08/brass-sorting-part-one.html

The results were pretty interesting, and I was surprised by a few of the findings. I hope that it's high quality enough to justify the time you spend reading it, and how much time it took me to create it.

I'd love to hear your feedback and answer any questions!

 

[Sheldon N]

Very thorough analysis. The one thing that would be interesting to see is if you could correlate the weight/volume with either actual measured velocity from each case, or with vertical POI measurements at distance if you did something like shooting paper at 1000 yards or a shot marker target. The Quickload estimate is good, but when I did this analysis before (someone else did the work, I just ran the numbers for them), we had a hard time correlating the weight/volume to measured velocity.

 

[ammolytics]

Very thorough analysis. The one thing that would be interesting to see is if you could correlate the weight/volume with either actual measured velocity from each case, or with vertical POI measurements at distance if you did something like shooting paper at 1000 yards or a shot marker target. The Quickload estimate is good, but when I did this analysis before (someone else did the work, I just ran the numbers for them), we had a hard time correlating the weight/volume to measured velocity.

Agreed, and I have it listed in the next steps section, so I'll tackle that in the next part of the series!
I'm certain that I have some velocity numbers for most of the times I fired these, but not all of them. I didn't want things to get too confusing up front.

 

[spife7980]

Ive always wanted to be this meticulous and focused but I just dont have the patience. The first cleaning I dump them all together and any sort of tracking goes out the window. I applaud your determination as much as the data ?

 

[Deleted member 113831]

I notice that there is only a 2 grain variation in your cases. Someone using LC in 308 would be dealing with more like a 6 grain or more variation in case weight.

I have run some simple experiments in the past with a wide variation in 308 cases and Varget. I used some Hornady, Winchester, Remington, Federal, Lake City, and RWS cases.

On the light side, Hornady weighed in the neighborhood of 150 grains, to RWS which weighed close to 180 grains.

Long story short... I used a conversion of .04 grains of Varget per 1 grain of case weight. To test the theory in the extreme, I loaded up 3 of each brand of case using the .04 conversion factor. I was able to keep extreme spreads in the vicinity of 30 fps at 50 degrees F.

It is interesting to me that you show no discernible difference between cases of 2 grains difference in weight. I used to sort my LC cases into batches by 2 grain increments. I too found it too fine an increment. I do still sort into heavy and light though, which amounts to a little more than a 3 grain increment.

It makes me feel better anyway.

 

[Rocketvapor]

I sort then segregate the outliers, usually 2 or 3 per hundred.
How do they shoot? Dunno, use they for dummy rounds.

(I actually do sort cases, bullets, but not primers. If I admitted it though I would really catch it on the hide)

 

[ammolytics]

I notice that there is only a 2 grain variation in your cases. Someone using LC in 308 would be dealing with more like a 6 grain or more variation in case weight.

I have run some simple experiments in the past with a wide variation in 308 cases and Varget. I used some Hornady, Winchester, Remington, Federal, Lake City, and RWS cases.

On the light side, Hornady weighed in the neighborhood of 150 grains, to RWS which weighed close to 180 grains.

Long story short... I used a conversion of .04 grains of Varget per 1 grain of case weight. To test the theory in the extreme, I loaded up 3 of each brand of case using the .04 conversion factor. I was able to keep extreme spreads in the vicinity of 30 fps at 50 degrees F.

It is interesting to me that you show no discernible difference between cases of 2 grains difference in weight. I used to sort my LC cases into batches by 2 grain increments. I too found it too fine an increment. I do still sort into heavy and light though, which amounts to a little more than a 3 grain increment.

It makes me feel better anyway.

As I noted in the article, this is just the first in a series -- a starting point. The Next Steps include comparing more cases of different brands, such as Lapua and Hornady, where I expect to see different levels of variation.