Dillon 550 reloading 300 Blackout

[DizzyJ]

Update! Changed to a Forster micrometer seating die all issues fixed. Damn I feel stupid!

Any idea what was actually causing the problem?

 

[JJE76]

Any idea what was actually causing the problem?

I think my Hornady seating die was still crimping a little even when it was adjusted. Little bit of pressure was pushing the brass once I got below 2.20 coal. 2.15 length went perfect on the Forster.

 

[DLS]

I think my Hornady seating die was still crimping a little ...

I'd bet money that is the issue.

Change presses and you have to change die settings unless the distance from the shell plate to the top of the press (where the lock ring bottoms out) is exactly the same.

They rarely are, even with the same model of press.