A-Merc sucks and should be culled by hand. it slows down the reloading process but is necessary--as i think you would now agree.
to fix--a dremal is how I've done it before. be careful how deep you cut but any slight damage to the expander can be sanded and buffed out.
dillon will replace it but you can fix it faster than the mail.
hope you both do well this week end.
---no dremal? cut the case on a 45 degree with a copen blade or a hack saw.