As already suggested once-shot LC brass is not all equal. Machine gun shot brass is pretty stretched out.
The brass I got was from a National Guard rifleman's training range. No machine guns there....unless you want to call fully automatic AR designs machine guns. If you can find a source for that, you have as good as you can get, unless you can swing the price for new unprimed & uncrimped LC brass available from some sources like Grafs, Midway, and others at times.
THR's GW Starr & Arfcom's GWhis is me. Wasn't smart enough to see the advantage of one signature across forums when I joined.--GWS