Design: Blastshell Variant A [6+1, 3, 2]
The most difficult part about blastshells, as it turns out, is the power density. We HAVE the technology and know-how to build the shells, but our magi-tech isn't quite there to make them feasible.
We manage to produce a working example for the HA1, at least. The large size of the shell gives us room to play with, in order to fit in the modest copper scroll-work and A-level magegems. AA proved to be too weak and and we required too many to fit in the shell, so A-level gems were used. Two A-gems were required for a SPSF-C blast, so for a larger-scale PSF-C we require three times as many. A nickel circuit controls the spellwork, measuring both the force exerted on the shell and using a cheap AAA gem for a split-second timer.
The shell itself is a solid iron slug. It has the copper scroll for a core, which is integrated with the 6 A gems and single AAA gem. Because gems tend to slowly discharge over time, the cores are removable and are charged and inserted only when it's time to fire. A small cup-shaped indent in the rear of the shell gives the concussive blast a direction to fire in and appropriately apply the force.
When fired, the blast of three simultaneous PSF-C's triggers the sensor, which begins draining the AAA gem. Once empty, the six A gems are all simultaneously drained to conjure a single additional PSF-C in the rear cup of the shell.
The end result is a shell that gains an extra "kick" a split second after leaving the muzzle of the cannon, propelling it even further and faster than before.
The shell proves to be rather inaccurate once it reaches lower speeds, unfortunately. The inclusion of the cup on the rear of the shell manages to capture the extra power of the blast, but induces quite a bit of turbulent drag - especially at low speeds. The shell can reach BLOS+1, but accuracy at this range is non-existant. Additionally, the fact the shells need to be charged before firing slows down firing rate, although not to a large degree. But hey, at least they don't jam the guns, right?
The shell is only available for the HA1, as it has the largest shell and we can fit the spacious circuitry inside it. The magegems are the most expensive part of this invention, making it Very Expensive.