NOT a C6 or B6 nozzle.
The B4 has the same diameter larger nozzle of the B14 and can be converted to pseudo B14s.
If you try porting/coring the propellant of a B6/C6, all you get is equivalent to an M80.
The smaller nozzle overpressurizes.
You cannot ream/drill the B6/C6 nozzle larger either. It crumbles.

__________________
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, and HAVOC !