I am also considering .223 for F Class.  I ran some numbers to see how twist affects stability.  I used Sierra Matchking as the benchmark.  Here's what I came up with:
69gr needs 9 twist
80gr needs 8 twist
90gr needs 7 twist
				
			69gr needs 9 twist
80gr needs 8 twist
90gr needs 7 twist
 
	








 
 
		 
			 
 
		
 
 
		
