weighing brass and water capacitys

[rogn]

I just read thru the post on weighing brass and had 2 questions, first if your going to weigh brass especially if your going from say a 6br to a 22br would it not make more sense to form, including fireforming and final uniforming beore weighing? Second if 2 cases are from hte same lot of brass and are uniform in dimensions, how can there be a difference in the water capacity?

 

[rogn]

I can see how a piece of brass can have a ding in the side and Id guess most do, but if the ding is superficial as most are, then the water capacity is finally identical. If the water capacity is not the same then there must be some sort of artifact remaining, such as a dent. ?

 

[amamnn]

I've been told that the distribution of the brass in the case has an effect on capacity. A case with a lot of brass concentrated at the head might have more capacity than a case with thicker body and shoulders, even though both weigh the same. Dents aside, and to some, all reason aside, case volume does vary, even in cases very closely controlled in the,FL) sizing process. The amount of variation might or might not be noticed downrange, depending upon how extreme the variation, how closely other variables were controlled in the loading process, and how long the range is.

 

[rogn]

IFF the brass is uniform alloy, IF the case dimensions are the same,rim thickness, extractor groove etc), IF there are no bubbles in the brass then the volumetric capacity cannot vary and there is more likely a variance in the measuring process, rather than the case. For all the work involved it'd make more sense to log each shot/case and segregate brass that way.

 

[USAPatriot]

IFF the brass is uniform alloy, IF the case dimensions are the same,rim thickness, extractor groove etc), IF there are no bubbles in the brass then the volumetric capacity cannot vary and there is more likely a variance in the measuring process, rather than the case. For all the work involved it'd make more sense to log each shot/case and segregate brass that way.

I think you're assuming that because the outside dimensions of two cases are identical that the inside dimensions must also be. If the two cases weigh the same you might conclude that. Yet when you measure case capacity with water, clearly the inside dimensions are not alike.

If you take a look at JB's photos in the Ultrasonic cleaning thread,s), you can see the effects that firing have on the inside cases. I beleive there's a minute amount of brass being lost with each firing. Spread that amount out over the 6 or 8 or 10sq inches of inside surface area and you can see how volume can increase with time. Brass growth, too isn't necessarily uniform from case to case and we trim it away eventually, again altering the volume of the case. All in all this isn't something you want to give a great deal of thought to unless you're willing to deal with it -Rod-

 

[rogn]