From: Phil Payne 

> What is a "ball bearing gun?"  BB gun?  Slingshot?

The ones I've heard of are magnetic - a series of coils around a
non-ferrous tube, each triggered by a photocell to attract (for a very
short period) an approaching ball bearing and then switch off so as not to
slow it as it approaches the next coil.

Large, long, immobile and much used in research.

--
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803
  +49 173 6242039

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