firefox - Spring boot Cache-Control static resources different behaviour mozilla / chrome -

this response

cache-control:max-age=300 content-length:542600 content-type:application/javascript date:fri, 28 jul 2017 12:00:27 gmt expires: last-modified:fri, 28 jul 2017 08:50:37 gmt pragma: 

now when static asset requested chrome browser response.

request url:http://localhost:9292/scripts.f9cd6b0fb5e6f4b9f51d.bundle.js request method:get status code:200  (from memory cache) 

but firefox

get : status 304 cache-control "no-cache, no-store, max-age=0, must-revalidate" pragma "no-cache" expires "0" last-modified "fri, 28 jul 2017 08:50:37 gmt" date    "fri, 28 jul 2017 12:02:38 gmt" 

i realize request sent backend :

if-modified-since "fri, 28 jul 2017 08:50:37 gmt" cache-control "max-age=0" 

but why need if-not-modified @ all? why not serve cache if firefox can see cached asset valid.

the result of app loads considerably slower when using firefox chrome.

is there way around ?