There will be 3 sets of bolts connecting the bulkhead to the nose cone and/or the AV bay.
The first are radial bolts along the base of the nose cone that connect to the bulkhead. These will have to withstand forces from two sources: the piston and the acceleration of the rocket. So, we need to find the approximate maximum forces due to both (with a safety factor of 2), and use the greater force to determine which arrangement and size of bolts we'll need.
First, the maximum force from the piston. According to recent sims, the maximum force it'll exert on the whole system will be 2250lbs during main deployment. However, the nose cone only feels its inertia, so
F_nc_section = F * M_nc_section/M_whole_rocket.
Currently, the mass budget of the rocket has a dry mass of 79 lbs. Assuming that the
M_nc_section = M_nc + M_nc_tip + M_nc_extension = 5.6 lbs,
then
F_nc_section = (2250lbs)*(5.6lbs)/(79lbs) =160 lbs.
Applying the safety factor of two and adding a couple pounds to the nose cone in case it goes over its mass budget,
F_nc_section = (2250lbs)*(10lbs)/(79lbs)*2 = 570lbs.
Next, the force due to acceleration. According to recent sims, the greatest acceleration will be when the entire rocket goes from 0 to Mach 4.09 in about 8 secs. Assuming a temperature of 30°C (86ºF),
Mach 4.09 = (349.02 m/s)*(4.09) = (1427.49 m/s).
That's an acceleration of
(1427.49 m/s)/(8 s) = 178.44 m/(s^2),
which is approximately 18.21G.Rounding up and applying the safety factor of two, we can expect an acceleration of 50G. The bolts on the bulkhead have to be able to withstand the force of everything attached to the bulkhead (AV tower, piston, recovery, NC assembly) accelerating with the rocket. Assuming they weigh about 50lbs and accelerate at 50G, then the
F = (50lbs)(50G) = (22.68kg)*(490 m/(s^2)) = 11113.2 N = 2498.35 lbs.
So it's clear that this will be the maximum amount of force that the bolts will have to withstand.
To calculate the arrangement, number, and size of bolts, we'll analyze the shear strength of the bolts.