Brass Working: One Way to Look At It

[Phil3]

For this novice, I have learned a huge amount from this site, and always feel compelled to contribute something back. I just hope it is of some interest or use, so here goes.

I have read much about “working the brass”, and decided to explore this further and add some quantifiable values to the discussion. My test:

Equipment
1) Virgin Winchester cases, fired 1x.
2) Fired from an AR-15 chambered in 223 Remington.

Neck Diameters
Fired Brass = .254.
Full Length Resize w/o Expander Ball = .239.
Neck shrinks down by .015.

Full Length Resize w/Expander Ball = .246"
Neck expands by .007 (from resized dimension above, .239).

The total change in neck diameter, from the necking down (.015”) and expanding up (.007”) is .022”. But just how “much” is that? If the neck is "unrolled", the amount of compressing and stretching of the brass is easier to see. That is, imagine cutting off the neck, cutting a slit lengthwise, and then unrolling it into a flat strip. The lengths would be as follows (assuming a diameter of .247, not critical for this test).

Neck “Strip” Length
1x Fired Winchester Brass = .798”
Full Length Resize w/o Expander Ball = .751”
Full Length Resize w/Expander Ball = .773

This means that upon resizing the 1x fired brass, the FL die will manipulate that .798” long piece of brass and shorten it by .047”. That is a shortening of its length by 5.89%.

After the shortening, the expander ball will then lengthen it to .773”, an increase of .022”, or 2.93%.

I am not an expert in metals, but this seems like quite a bit of metal working going on. Obviously, brass that lives in tighter chambers will have a much easier life.

Phil

 

[JeffG]

That's good work, and a new perspective on the concept of working brass.

I might encourage you to add neck wall thickness, and case length into your calculations. Then we would know where the brass going when it moves.

 

[firearmdoc1]

That puts things into a whole new perspective. Never would have thought of it that way.

 

[Phil3]

That's good work, and a new perspective on the concept of working brass.

I might encourage you to add neck wall thickness, and case length into your calculations. Then we would know where the brass going when it moves.

The starting neck wall thickness (new Winchester brass) was around .012". The fired brass was all over the place, but appeared to be THICKER. Such as .015" or more. However, this was AR15 brass, with dinged, scratched, and a bit dented necks, so the indicator was jumping all over. I want to try this test again with brass taken from a bolt action that should be in better shape. My first bolt action should be on its way back to me soon.

I don't know how to measure volume, so looks like something else for me to learn.

Phil

 

[Shynloco]

Phil,
Neat study and thought provoking as well. Now I can't claim much expertise in any of this and in reading books by Mike Ratigan and Tony Boyer, the single issue of "variables" comes to mind after reading your efforts. But there are two potential variables in your study that make me wonder about the "what if's."

1. Can your figures and conclusions change merely by changing the pressure exerted upon a casing by a lesser or higher amount of powder load and each different chamber they are shot in ? Also, the issue of pressure (as I see it) can be altered by merely changing primers.

2. What if you change brass manufacturer (for the same caliber) and the wall thickness is fatter or thinner AND will that have an effect of your conclusions?

I try and be meticulous in each step of the "reloading process" (to the point of being completely ANAL) and which some say a specific step may be a complete waste of time in trying to control a specific variable. Hence, I believe my two aforementioned and listed variables could alter even a carefully thought out proposition as you have done.

Great job either way. Thx!

Alex

 

[TC260]

The volume of the neck is straight forward, calc the volume of a cylinder using the OD and then subtract the volume of the inner cylinder using the ID (bad explanation sorry but I'm short on time). The volume of the shoulder area is a little trickier.

I don't have a materials book with me but IIRC, the basic formula for percent cold work is %CW = (Ao-Ad)/Ao x 100. Ao is the original cross sectional area and Ad is the cross sectional area after deformation. Just thinking about it here if the top of my head, the equation is simple but getting good measurements may not be so easy. Probably would have to do multiple firings without trimming and if material is flowing into the neck from the shoulder that may horse things up too.

 

[Phil3]

Phil,
Neat study and thought provoking as well. Now I can't claim much expertise in any of this and in reading books by Mike Ratigan and Tony Boyer, the single issue of "variables" comes to mind after reading your efforts. But there are two potential variables in your study that make me wonder about the "what if's."

1. Can your figures and conclusions change merely by changing the pressure exerted upon a casing by a lesser or higher amount of powder load and each different chamber they are shot in ? Also, the issue of pressure (as I see it) can be altered by merely changing primers.

2. What if you change brass manufacturer (for the same caliber) and the wall thickness is fatter or thinner AND will that have an effect of your conclusions?

I try and be meticulous in each step of the "reloading process" (to the point of being completely ANAL) and which some say a specific step may be a complete waste of time in trying to control a specific variable. Hence, I believe my two aforementioned and listed variables could alter even a carefully thought out proposition as you have done.

Great job either way. Thx!

Alex

Alex,

Thanks for those comments. I have made note of your suggestions and will test most if not all of the variables you suggest, when I get my bolt action rifle back from the gunsmith. The AR-15 is just too rough on the brass, making measurements far more susceptible to error. I have to work up loads for the bolt action, so that will be a good time to check varying pressures and impact on the test I performed. I have a lot of Remington 7-1/2 primers, but if I can find some others, will try those out as well.

I think a change in brass may have a significant effect. I have Winchester and Lapua brass to experiment with.

I will report all findings once I am done. Right now, I am waiting for the rifle to get back, and also spending time looking for a job.

Thank you again for your feedback.

Phil