9mm COL

[jmorris]

What can cause this amount of variance?Given this recipe, is the .015 variation significant enough to make these rounds unsafe?

I don’t have an answer on the safety question but Speer did have a load combination that more than doubled the pressure with .030” difference but they didn’t share what that combination was but I would file it in the “unsafe” category.



As for the inconsistencies, not operating the press the same for each and every stroke, the bullet and seater don’t like each other, the bullets themselves can vary but I doubt by .015”, then again is possible even that measurement is not accurate.

Depending on how one measures a high primer could add to an OAL measurement. Even if there is no fault in the other processes.

The closer we look at things the more we can learn though.

The crimp is set with the seating die, nothing excessive…I'm loading a mixed batch of brass. I haven't messed with my dies. The vast majority of my loaded rounds COL is 1.060.
However, some have come up as short at 1.045 and as long as 1.070.

I would focus on the odd ones. Is the case wall thicker than average on the long ones? So you are increasing the force required to move the handle to the same position.

Are they a certain head stamp you can avoid in the future because of this?

If you sort by headstamp (you can do this after loading if you like) are the results more consistent?

Is there a specific brand that makes up the oddballs, for example?