Home Forums Hunting & Shooting Ask The Gunwriters Weight variance in brass?

One problem with measuring water capacity of different kinds of brass is variation in how much cases spring back after firing, even when fired in the same chamber. This can vary with brass thickness, how many times its been fired, and the exact alloy. As a result measuring capacity is by no means exact, and case weight is a better indicator of capacity.

Indeed, see edit!

From another thread:

I know nothing of metallurgy, but what about the possibility of one batch of brass being denser (and heavier) than another, with little variance in internal capacity between the two?

I was recently given a quantity of Remington once-fired 6mm Rem. cases from the 70's. All were in original cardboard boxes and there were several different lot numbers on the boxes. I separated the brass based on weight. The lightest averaged 173 grs, the heaviest 188 grains.

Using a moderate load (43 grs. Reloder 19 with a 100 grain Partition, Federal 210 M primer) chronographed velocity for the light cases averaged 2806 fps. The heavy brass averaged 2812 fps; virtually the same. Loads were fired in a Cooper with 22" barrel.

I have not yet checked the water capacity of any of the brass.

It would seem prudent to sell that lot of brass to someone who does not already run Nosler headstamps. No sense to waste it all.

Yup. Some brands are not only softer,but vary in head design and web thickness(taper) as well. Remington has always had this "reputation" for being thicker and softer than WW brass,which seems generally lighter and harder.

Point being brass varies from one manufacturer to another. This can be a royal PITA if you don't have enough of one lot hanging around. Good to back off your load and work back up when changing types (makes) of brass.

That was exactly your question, you never mentioned pressure in your original question.

"That much is understood. The question is, does a 5% variance in weight translate to a 5% variance in volume."

Volume and pressure are not the same thing...

As to the thread title as it appears on the forum list: the left one is usually a bit larger/heavier.

Is that you Sherlock?

I treat new brass as brass that needs to be fire formed to the chamber. Case volume is determined with the unsized fire formed case. A powder charge is chosen and chronographed, cases are 'sized' withal Lee collet die and tend to stay the same dimensionly until the shoulder needs to be bumped back, generally this takes many firings before this is needed.

Hers, or yours? And her left, or your left?

Thnx MD - Yes, I understand there are other variables.

Yrs. ago I experienced a problem w/a lot of brass. Long story/short. I was shooting 62 grs of SURPLUS 4831 in NEW 270 brass and LOST 200 fps. There was NO room to add more powder so...
Never figured out what the problem was so I trashed them BUT at the time the cost was NOT $1.00 ea.


I asked Sam if he 'could' compare them not only by new weight but also filled w/water just to have a better idea of what he was working with.


IF those NEW brass were mine, I'd probably back off the powder charge by 2 grs. (probably more than enuff) and work back up by 1/2 gr increments and whatever charge worked best, I use in that 'specific' lot of brass.

Just what I would do.

Thnx Again

Jerry

I've always liked that 4 to 1 rule.

WRT to water weights, I suspect you do the same thing as I do, John. There are circumstances when I measure dry and wet case weights with new or new to me brass, or for cartridges that I've never loaded. I trust case weight absolutely (no primer). I trust water weight (when I measure it) almost as much. But...

I only trust me. Since I do it the same way each time, there is less divergence. I trust my method of filling a case and leaving a very slight concavity. Using someone else's measurements will mean more variance, since we may not add water in the same way.

I know some people overfill cases. Surface tension allows them to fill them to the top and a tad beyond. It's another variable, combined with different case brands or brass runs, that can produce different results.

Then there were chamber sizes. Once upon a time, I used to take 20 new cases and check water weight before and after firing. Wanted to see how cavernous the chamber was by comparing the 'before and after' volumes. Somewhere along the line I realized that I was getting too anal. I also realized that there were variations the the brass that would produce slightly different results. I don't bother anymore, unless I've got a reason.

All that said, for my personal hunting loads, I don't care. I simply stuff cartridges with propellant and verify on paper at different yardages.

Thanks, Sam for pointing out that makes of brass can vary by lot. Hadn't run into that.
A couple of things I've noticed.
Even with brass that can vary alot, if you don't go for the highest velocity possible, one can load ammo with different brass weights that flies the same over at least 300 yds.
Factory ammo can also vary, not only in velocity, but in the rifle's zero. If you hunt with factory ammo, it's a good idea to buy 2-4 boxes of the same lot number. E

E -

Just an intended helpful suggestion.

All components in reloading CAN vary from lot - lot.

Brass, Powder, Primers, and Bullets as mentioned in this thread.

Take nothing for granted. Check and Verify. It's not just for accuracy, SAFETY can also be involved.

Jerry