The problem is 21:41:03.589 [script.load.notFound]: ***** Could not find a script file named railgun-firing.js. - you're missing a file somehow in your OXP installation. Either something has gone wrong in the filing or when you unzipped/installed it (perhaps it got eaten by your anti-virus program?).
I'd try downloading it again and then carefully unzip it and make sure that there are no errors and that all the files are in the folders they should be (scripts should be in a "Scripts" sub-folder).
Also from the log you're missing Cabal Commons - BGS will not run without it.
Editted to add - Your follow-up comment is correct - see above. There should be two files in the folder, railgun-firing.js and railgun-projectile.js
Oh and Galactic Navy OXP is also I think currently orphaned and is a little bit outdated and has a few problems (as you can see from the log). It should run, but may not be without issues.
Would certainly recommend grabbing Cabal Commons Library - BGS is well worth it.
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You're welcome. 
