not sure how many attempts I've made. 6 or 8 I think
 I use a 28"x 36" white poster board with a black shingle in the center and just record pertinent info next to each shot with a sharpie for posterity. 
 I find it helpful having every shot on the same board.   
 I'm planning on a session Friday or sat or Sunday  , 1 of those days at least.  
 I'll post a pic of my current progress . 
 by the way I would be quite impressed by anyone hitting that speck of a target at 100 yds.  cold bore. which I plan to do!  

good luck shooters
kevin