Testing many items from feeder over a few shared connections

I need to test 500k ids from a feeder over a limited number of shared connections, however the test only uses as many ids in my feeder file as I have users set in my load test. Since gatling users corresponds to connections, pushing the number of gatling users to 500k doesn’t make sense, I only want 400 connections opened to load over thousands of ids.
How can I test 500k ids in a feeder and only open 400 shared connections?

Here is the code below I am using, that is only using 400 ids from a feeder file of 500k in the actual test.

val httpConf = http
   .acceptEncodingHeader("gzip, deflate")

I am using Gatling 2.1.7 by the way.

You can share the connections amongst virtual users: http://gatling.io/docs/2.1.7/http/http_protocol.html#connection-sharing