Just found the answer and bottle necked cartridge is a 45 Colt blank.
These were designed to be in the 45 Colt revolver for a more effective report.
So mystery solved.
Need some help identifying this Pre WW1 cartridge that was found relic hunting and found large amount of buried ammo in Fort Oglethorpe GA.
This is a blank cartridge and all the others that was recovered like this was all blanks unfired.
What I do know is it is Frankford Arsenal from 3 1910...