I posted another thread regarding some unfamiliar .308 brass that I received from a friend and got some great info back from several folks on here educating me on the brass...

That brings me to the next question(s) that I have in trying to use the boat load of free brass that I got.

I am (was) concerned about the consistency of the Prvi Partisan (PPU) brass so I weighed a batch and was pleased to discover that the brass weight varied less in this brand than the usual Winchester brass that I have been reloading. The greatest difference I found was 2 grains, where as the Winchester brass varied as much as 3.3 grains.

So, being new to all this, that leads me to be concerned about the amount of internal volume in this PPU brass...Can someone explain to me how to best compensate for this issue? I am sure that this will affect pressure and how I should load them. Is there a rule of thumb for this situation? Thanks in advance for any info!

Most folks will advise that you weight the cases full of water, and so many grains of water vs so many in the other brand case. To me I have always found that a dense ball powder would answer the same question without all the mess. Just be sure both the cases have been sized the same and are of the same length. Weight alone cannot tell you which case has greater space within, but it does help on uniformity issues.

In general Military brass has less internal volume. Most reloading data sources suggest a 10% reduction in powder charge. As usual, Start low and work up your load. Keeping an eye out for pressure indications. Stop when you reach an accurate load for your rifle, high pressure signs appear, or you reach maximum load for these components. Which ever comes first.
Sounds like a reloading manual. Yup and its great advice.
As an aside the mil surp 5.56x45/.223 brass is very close to commercial brass internal volume.

muck

Your chamber is your pressure vessel. Brass has a certain density. Therefore, (in practical terms) all of the brass you put into the chamber has to be subtracted from the capacity of the chamber. Thus, however much more one piece (brand) of brass weighs than another is the difference (converted to units of volume) in the capacity of your pressure vessel, ie. "powder capacity".

One caveat: Brass can vary in the thickness of the rim and and the size and depth of the extractor groove. This can usually be discounted as deminimus, but could theoretically represent brass volume in the case that is not deducted from the effective volume of the pressure vessel.

Measuring the internal volume of an unfired case, or cases fired in different chambers, or cases resized to different degrees in different dies is a somewhat meaningless excersize. What you want to know is how much space is left inside the case when it is fired and is pushed fully outward against the chamber walls. Knowing its unfired static volume is much less useful.

I bought some graffs headstamp brass that I think was made by the same company. In my 308 I load that stuff down about 1.1-1.5 grains from win brass and it clocks the same speed.
I would give you a recomendation that unless you are running win brass at max loads that you start about 2 grains under and work up to the speed you are used to seeing in your favorite brass.

I wouldn't get too excited about it. If you already have a good load and the new brass is heavier that the brass in which you established the good load, then back off around 5% and see how the new brass looks at that load level. Then work up (or down) as needed.
If you're starting from scratch, then (no pun intended) start like you developing a load from scratch.
I wouldn't spend too much time angsting over a grain or two of case weight unless your current loadings are at the ragged, red edge.

The main problem I have with 308 case volume is the charge for the threshold of long brass life changes.

If you get 3000 fps with 150 gr 22" barrel, you don't have long brass life anyway.

If you have 2500 fps with 150 gr, a slow powder, and 22" barrel, the brass volume will not matter. You always get long brass life.

But somewhere in between, there is a threshold.
When I switch from Win brass to LC brass, that threshold drops down a grain or two.

Brass is 8 times more dense than your typical powder. So it takes about 8 grains of brass to take up the same volume one grain of powder takes.
Just to put the question in perspective.

Thanks everyone for your input. I appreciate the information.

For years fussy benchrest shooters have said you need all cases from one lot, or it's crap. A number of years ago when I wrote for Precision Shooting, I also shot Hunter Class benchrest. Full length 308, 150gr Sierra MKs. 3/4" 10-ring at 100 yards, max 6X scope. A Colorado guy took seven pieces of pick up brass at his local range and turned the necks and trimmed them to length. He shot seven perfect scores in a row. So much for the brass consistency issue...

Rich
Buff Killer