It was a 20 caliber, I don't remember what cartridge, probably a vartarg. it's not about getting them to line up, more offend than not, it's about bullets fragmenting like a grenade. It was about 75 yards. 32gr vmax. these were belding ground squirrels in No. CA. if you are lucky enough to be there the day they come out of the hole for the first time, they will line up or gather around the hole. they can have 11 or more babies per mother. it's been my experience, you have a one or two day window to catch them on their first day out. after that, they are out and running around every where, still good shooting, just not the same grouping.