Sounds about right, particularly with the smaller motors. The majority I have seen, though, have been of the Alien CATO variety. And when you are talking about K and up motors, it gets real ugly real fast. SssssSSS..BOOOM! Seen stainless blast deflectors twisted up by whatever comes out of the bottom of the self destructing motor hitting them.
Drawback of the system, as the forward motion of the motor is checked by the rear closure. If it comes off, there is nothing to prevent the motor from going forward (unlike, say, brand K motors that have an external thrust ring separate from the rear closure).