New Vs once fired brass

[Dennis Filipowski]

Just today I came across a confusing and frustrating situation.

I bought some of the new 9mm brass from RMR. Have been loading and they ran very consistently.

Today I wanted to compare the results using the once fired I have was using prior.

All looked good until I checked the COLA. The once fired brass length was 020-.025\” less.
Did several rounds with used brass. All much shorter.
Grabbed several new brass cases and they were perfect at the COLA I set previously for the 9MM.

Why would new vs used brass run so different?

9MM 124 gr MW bullets

[SC]

As long as it within SAAMI spec, why worry about it?

[Author]

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