I believe these solenoids would need to be controlled, They aren't designed to automatically auto-fire. The Time Crisis guns are controlled, for either semi-auto, or automatic fire based on the gun you are using in the game. I wouldn't know how to trigger the desired results, my expertise isn't circuit design, but I'm sure of two things: These would work, and they're small enough to fit in the smallest guns in the Halo universe. They would be ideal for creating a 'real' recoil kick. They're powerful, in other words.
In my mind the ideal gun control board would do the following:
Control solenoids for semi-auto and automatic fire (maybe a dipswitch setting on the board?)
Control LED's times to fire with the simulated gunfire (for muzzle flash
Control a audio playback unit with recording and playback capacity (preferably with a input jack for quality recording)
with the optional Ammo counter... for guns like the AR and BR
And the trick is that all these need to operate simultaneously with the trigger pulls.
Other weapons would require custom units (like the carbine would need sequenced lighting instead of an ammo counter) to simulate the covenant display on the gun. Guns like the magnum and SMG's would only need recoil, sound, and muzzle led's, no counter.
Have you guys ever seen the control boards for pulse rifles?:
http://www.aspeng.com/Pulse_Rifle.html
We need something just like that unit, but with the option to set the ammo counts for the various weapons..