I've got one,...................... they work and work just as advertised,the BDC marches the bullet right up the paper,it's real simple to use,kind of like the square peg in the round hole drill. Match up the circle to the brisket and withers and ka POW! the work will begin.They actually make them in a little town where my buddy lives.................. Shepherd MT.He's building a long range shooter and is going to shepherd it up.