I take it from your question that you have a right hand or power feed shocker.
you should not need a ball detent on a shocker, if you are finding that balls are rolling out of the barrel then it would point to a wrong paint to barrel combination. This is one of the reasons that smart parts created the freak system.
a ball detent will not stop the ball rolling out of the barrel because the shocker works as a closed bolt system so the ball is in the mouth of the barrel before it is fired. A ball detent may help with double feeding but again can be cured on a shocker by setting the timing correctly. So unless you have a vertfeed body then is no real point to having a ball detent on your shocker.
cheers
Bruce