100% sure a squib won't cycle an action totally?!?!It would stop your bump fire and then you would have to rack another round into the chamber, squibs usually don't cycle the action fully, if at all, they just kinda make a small pop sound but no bang and no cycle. Bump fire relies on the rounds going off properly and cycling the rifle, if they don't go off, the rifle won't cycle.
Tap rack drills have their place. Once upi start shooting wth a more defined purpose, yuo'll see where they come in.