Is an MFR grinder incapable of killing a wither boss?  I've tried it from a few locations (low/high) and when the cycle eventually comes around the wither doesn't take any damage.  Eventually it gets bored and shoots a couple of times and blows the grinder up.
				
			 
				
		 
 
		 
 
		
 
 
		 
	 
 
		 
 
		 
 
		
 
 
		
