Why not a "Mini/Gatling-gun" type set-up, with rotating barrels. Then all it would have to do is pull about 6 "Box Cars" (as Framer said) of ammunition.

The Japanese and their suicide personel had the most effective/economical means of destroying tanks (credited with 1/2 total losses on Okinawa/Iwo Jima), though distasteful/morbid, not to mention all to final for the attacker.

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Morbius, Morbius! Something is approaching from the Southwest. It is now quite close.