There were several protypes built by MIT grad students. Mass driver 2 used superconducting magnets in a push pull setup, details and all the math has been published.

While it is possible to levitate a spider via paramagnetism it is beyond current magnet technology to toss it at 4000 feet per second. O'Neill's magnets produced a couple of tesla current magnets are up to 35 tesla.

The actual prototype was a foot or so in diameter and 2.5m long it accelerates non-ferrous materials such as Plexiglas or potato by way of a carrier bucket, there are photos of the original on the net. I suspect that a frozen potato will not vaporize although it may cook in flight

Try freezing with liquid nitrogen




Construction and testing of the 2.5m mass driver

SNOW, W. R.ONEILL, G. K. (Princeton University, Princeton, N.J.)
AIAA-1979-2095
Princeton University, and DGLR, International Electric Propulsion Conference, 14th, Princeton, N.J., Oct. 30-Nov. 1, 1979, AIAA ...

Has anyone considered building a spudgun using Gerald O'Neils mass driver plans.(he was a physicist and active in promoting space colonies) His prototype built from salvaged magnets from a particle accellerator would accelerate a chunk of 2" plexiglass rod (about the mass of a potato) from zero to ...