Probably a roll pin (1/16") ... please look closely to verify.  If it is, remove the barrel, bushing, etc and punch it through from outside to in.  Same setup as Dan Wesson.  If you properly fit and Loktite the new sight, you won't need it anymore.   
 
Mike
		 
		
		
		
		
		
		
			
				__________________ 
				Mike
 
Addicted to Pulling the Trigger!   
COTEP No. 0265   
			 
		
		
		
		
		
	
	 |