So I may have gotten a little excited today when starline announced that they now produce 30-06 brass! But then my M1 curiosity came out and I asked if the case capacity would match commercial or military specs. The techs said it was smaller than norma & hornady brass but had no idea about military brass. So they asked if I'd like a few to test... Hmm... Ah ya!

Now for my problem, how? I've seen where guys talk about using water, sand, rubbing alcohol, ball powder ect. How can I do this and get fair test?

Water volume test....

To get the actual amount yes water so that means you will have to prime them with the same brand spent primers and measure the water they hold...best to do that by weight or if you just want to compare them to the brass you have been using you could just prime them with spent primers a fill them with ball powder since it packs so well or you could use the powder that you use to load 30-6 because if they hold lots more it will be clearly evident when you fill a case with you loading and it is way short.

You're going to need to fire them in the same chamber as whatever other brass you're comparing them to, otherwise it doesn't mean much. Even then, brass spring back is different for new vs work hardened cases so it's not a very accurate measurement.

Personally I'd rather just measure the weight difference after firing and trimming them all to the same length.

Good thoughts.

It seems to me that you need to first decide whether you're going to full-length size or neck-size. If neck-size, then fire them all in the same chamber, then neck-size, THEN measure capacity. Or if you're going to full-length size, then size them all, trim them, then measure capacity.

That sounds logical to me . . . except for one niggling little thought. What's relevant, the case capacity at the moment you pull the trigger, or the case capacity a few milliseconds later as the case expands to fill the chamber? If the latter, then yeah you should measure capacity after firing and before any resizing, neck or otherwise.

You could be overthinking the plumbing. Start by comparing the WATER capacity of the new Starline brass to that of new commercial brass from another manufacturer. No sizing is needed.

Plugging the primer pocket with modeling clay might be a bunch easier than the spent primer route.

If new Starline brass is the same WATER capacity as other new commercial brass, then you have the answer. We already know how commercial brass differs from military.

I dunno, I don’t think measuring NEW brass is the answer, since you don’t know how the new brass is shaped. Some new brass will chamber just fine, some new brass needs to be sized before chambering. I don’t think “new” gives you a level playing field between brands.

So run the new brass and old full length through the sizer plug the primer one way or another and get it done. I am running a good half dozen brands of cases for 30-06 1000 total some dating back as far as as 1939. It took me a whole two hours to figure out the heaviest and confirm the smallest capacity and I used the smallest capacity to work up my load so as not not have over pressure.

I'm curious to know what brand of 30-06 brass (new) did not chamber and in what firearm that happened?

I’ve never bought new 30-06 brass. I’ve had it happen with 7.5 Swiss.

The first of those has some small effect (because it takes work=energy to form brass to the chamber), but the second condition is the important one. And, if you're trying to compare capacity of one brand to another, you want the case outer dimensions to be identical otherwise it's meaningless.