Yep. After subtracting the thread depth, a 7/8-14 die leaves you only about .75" to whittle out under the threads. Subtract the 0.560" SL1 measured from that and you have metal wall thickness of only about 0.020" left all around.
If you have a .50 BMG or a .577 Snider or other fat case, you need 1¼" dies and a press that will handle them.
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