Using only 3 C's on any 51" rocket is asking for trouble if it is anything over a BT-60 (just big enough for a 3x18mm cluster) in diameter. Anything this big is begging for at LEAST a full 40n-sec E if not an F.
3 Estes C6's don't even add up to 30 n-sec of total impulse.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !