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

Thanks John,

Good to know about the +/- 90fps SAAMI variance. 180 fps total swing, that could explain some sighting in stuff I've seen over the years. Now that I've got a chrono I should start using it more often. Always a bit of a pain on public ranges though.

Sam,

Thanks for bringing this up,

Good luck to all on their hunts and "woods loafing" this fall.

Geno

If the external dimensions are the same between two brands of case, then the heavier brass will have less internal volume. This is more critical with smaller cases than larger ones.

Because fired brass generally has more internal volume due to expansion, it is important to work up loads, record weights and internal volumes for each brand or lot of brass.

Sam.

At one point Remington was making brass for Nosler. I understand that is no longer the case. As Mathman mentioned Remington brass tends to run heavy. It sounds to me like you may have picked up a box of new/old stock Remington made of Nosler brass.

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

It is not a direct linear relationship. I imagine the internal variance would be about half that. The best way for Sam to find out is measure the internal H2O volume.

I was going say couldn't a guy just measure with water?

Nope. It does reduce case capacity but you can't calculate "new" case capacity that easily. You would have to convert the weight of brass to volume using its density, the deduct that volume from the "original" case capacity to determine the difference.

It's much easier just to measure the difference in case capacity by measuring case capacity of each by weighing the empty fired case then filling with water and weighing - in this case, a 5% change in weight of the water is a 5% change in case volume.

I dunno. According to some over on the Nosler forum, it's Norma that making Nosler brass. Never used the stuff so the other day I bought 100 pieces to try out. I must say it good looking brass. Primer pockets are nice and square, not like the concave pockets of most commercial brass. You can look down inside and see the flash holes are properly reamed to eliminate the burrs. Now if my .280 Rem. rifle likes the stuff???????
Paul B.

Also understood, but that wasn't my question.

The real question is how the volume difference relates to pressure with the same powder charge. Probably easiest to just load some up and shoot 'em over the chronograph.

i can tell you that with a max load if you switch from Winchester to Remington brass in a .270 Winchester you will need to drop back a grain of powder of you will be loosing primers

Thanks. Actually loading some RP 308 brass with a load worked up in lapua so it should be fine.

Sam -

I know you said you threw them in the trash.

Are they gone OR could you retrieve them?? and compare water capacities.

An addendum:

I could 'assume' those brass are GONE since you threw them in the trash.... but not necessarily so.

It has to be measured. There is no direct corellation or ratio. IOW, 5% more water volume does not mean you can put 5% more powder in.

That's been my experience as well. Have experimented some with different brass in the same rifle, and the amount of powder required to match velocity with two kinds of brass isn't always predictable, everything else being equal. About all that can be said is heavier brass normally requires less powder.

A lot of this probably involves the 4-to-1 Rule, where in any change in powder capacity in the same bore results in 1/4 that much change in velocity AT THE SAME PRESSURE.

J, retrieved and weighed.




Nosler 185 grains empty 258 w/water

Nosler 207 empty 276 w/water

Fed(old) 205 empty

Hornady 205 empty

W/W 193 empty

The lighter 'Nosler' brass holds 4 more grains of water.

I would have guessed more.


Wish I had Chrony data on the hot loads.


Nothing crazy I'm sure but maybe +100fps?

Also, its a good idea to check the interior volume of brass to get a base line. Any additional brass from different manufacturers or lots of the same manufacturer can vary. The volume does vary and its prudent to know what those changes are.
The Quickload program is useful in determining predicted pressure as related to case volume and powder charge.

No, it doesn't.

Thnx Sam

At &1.00 each, I'd have to swallow hard to discard.

I'd probably MARK that lot and load specifically for them. Yep, it sucks but maybe worth the time.

Good Luck

Jerry

Jerry, worse part is I got nervous for a day and started thinking I had a gun or scope issue. Deer season in a few weeks and all of a sudden what the hell is wrong with this gun or scope?

Until I finally wised up and noticed the primers.