Switching Brass brands....

[Koda]

Lets say you have a load you worked up but want to try a different brand of brass. I know that different brands have different internal volumes but I cant imagine it would be big enough to need to start over with a load development...
Is there a "rule of thumb" for reducing powder charge when switching to different brass?

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[JuglansRegia]

It depends, for low pressure pistol no big deal, anything at or over maximum recommendations could be a problem.

 

[Koda]

It depends, for low pressure pistol no big deal, anything at or over maximum recommendations could be a problem.

I would guess then the same for rifle?

 

[JuglansRegia]

I would guess then the same for rifle?

The higher the pressure and the closer you are to maximum, there is just less margin for change or errors.

 

[P7M13]

7.62x51 brass is thicker, which will cause higher pressures with the same charge.
I've also found that 7.62 brass will withstand higher pressures.

 

[Pepe-lepew]

7.62x51 brass is thicker, which will cause higher pressures with the same charge.
I've also found that 7.62 brass will withstand higher pressures.

Military and some commercial brass are thicker in 308/7.62x51. You can't even go by manufacture, Hornady has produced thin and thick wall 308 cases. Mixing Hornady head stamps could be the same as mixing heavy military with light commercial cases.

 

[po18guy]

Weigh the brass. With outside dimensions identical, the internal capacity is determined by weight.

 

[ron]

Pistol brass you can use mixed cases no problem reloading good accurate ammo. I have tested my match grade
223 loads using identical components except for type of brass. I have tested this many times and the with same outcome.
Winchester brass produces about half the group size as LC. The LC is all once fired same year fully processed.
Bottleneck rifle calibers accuracy (sub MOA) is dependent on uniform case neck tension. Talk to a long
range competition shooter about Lapua brass.

 

[Koda]

Weigh the brass. With outside dimensions identical, the internal capacity is determined by weight.

Yes, but what Im looking for is some metric to judge how much to reduce the powder charge?

Like say if the new rifle cases weigh 0.2g more then drop the powder charge by 0.2g....?

 

[Member 34319]

H2O.

You can measure the internal volume with water.

Plug primer pocket, however you seem fit. I use a tool. https://21stcenturyinnovation.com/buy-online/ols/products/primer-pocket-plugs

Measure cases before and after adding water. Math.

 

[gmerkt]

I can tell you that there can be differences beyond pressure considerations. Rim diameter. Some European brands vary. Someone will tell me, "They are made to CIP specs, not SAAMI.' That may be, but I have some from Serbia and some from Czechia and they take different shell holders.