Here are few examples of how much the powder capacity different brands of brass can possibly affect velocity and pressure.I used Hunter powder for this example because it's a powder I would use for 30-06 loads and also because it's a ball powder and I can get a more accurate case fill.It also a good way to get an idea of just what is the full maximum case capacity for the powder your going to be using.The cases I used were Remington 30-06,case weight was 200grs,Lapua 30-06,case weight was 194.8grs and Winchester 30-06,case weight 190.1grs.I filled the Remington case full of powder and that weighed 67.5grs.I then dumped the 67.5grs into the Lapua case and then into the Winchester case.You could see the Lapua and the Winchester case would hold more powder than the 67.5gr charge that filled the Remington case full.How much more?I could put two more grains of Hunter powder in the Lapua and Winchester case to fill the cases completely full.How many grains of powder you can get into a case will vary because powders are different.Some powders are heavy per grain volume and some are much lighter per grain volume.I could have never been able to get that many grains of an extruded powder because of more air space between the grains of powder.So I looked at Western Powders load data for a 30-06 using Hunter powder.They also used a Remington case for their load data.The heaviest charge they had was 68.6grs of Hunter with a 115gr Berger FBT bullet.Their Remington case must have had a bit more case capacity because mine was full at 67.5grs.I could have held that charge in the Winchester or Lapua cases I have,but it would have been a really compressed load to seat a bullet in a full case of ball powder.Hunter wouldn't be my choice for a bullet that light.I would rather use it for bullets around 150gr or higher.64.0grs will put the powder about the bottom of the neck.That's near what Western's shows for 150grs bullets and it will give plenty of room for seating the bullet.

67.5grs of Hunter in Remington 30-06 case
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67.5grs of Hunter in Lapua 30-06 case
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67.5grs of Hunter in Winchester 30-06 case
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~Molɔ̀ːn Labé Skýla~
As Bob Hagel would say"You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong."Good words of wisdom...............