Looking for more info on my grand father

Welcome to the forum Josh. Here are a few things to get you started.
First - the blue badge is called a Combat Infantryman's Badge (CIB)

Specific eligibility requirements

• (1) A soldier must be an Army infantry or special forces Officer (SSI 11 or 18) in the grade of colonel or below, or an Army enlisted soldier or warrant officer with an infantry or special forces MOS, who subsequent to 6 December 1941 has satisfactorily performed duty while assigned or attached as a member of an infantry, ranger or special forces unit of brigade, regimental, or smaller size during any period such unit was engaged in active ground combat. Eligibility for special forces personnel (less the special forces medical sergeant) accrues from 20 December 1989. Retroactive awards for special forces personnel are not authorized.
  (2) A recipient must be personally present and under hostile fire while serving in an assigned infantry or special forces primary duty, in a unit actively engaged in ground combat with the enemy. The unit in question can be of any size smaller than brigade. For example, personnel possessing an infantry MOS in a rifle squad of a cavalry platoon in a cavalry troop would be eligible for award of the CIB. Battle or campaign participation credit alone is not sufficient; the unit must have been in active ground combat with the enemy during the period.
  (3) Personnel with other than an infantry or special forces MOS are not eligible, regardless of the circumstances. The infantry or special forces SSI or MOS does not necessarily have to be the soldier's primary specialty, as long as the soldier has been properly trained in infantry or special forces tactics, possesses the appropriate skill code, and is serving in that specialty when engaged in active ground combat as described above. Commanders are not authorized to make any exceptions to this policy.
  (4) Awards will not be made to general officers nor to members of headquarters companies of units larger in size than brigade.
  

Combat Infantryman Badge

Second - some info on the 315th. 315th Infantry Regiment - World War II History (LoneSentry.com)

79th Infantry Division - 79th Infantry Division order of battle ww2

Third - Go here for details on criteria for the Bronze Star http://www.tioh.hqda.pentagon.mil/Awards/bronze_star.aspx

The bronze "V" identifies the award as resulting from an act of combat heroism or "VALOR", thus distinguishing it from meritorious achievement awards.​

http://www.homeofheroes.com/medals/pages_wh/10_bronzestar.html

 

Do you have his discharge papers? The Purple Heart details would be on it. If not, have you tried to get his data from NARA? Check this thread on details of how to go about it. http://www.ww2f.com/military-servic...esting-copies-military-personnel-records.html

Sometimes the documentation for various awards was not very thorough, but you can also request the After Action Reports (AAR) for his unit. You might find the information there. Go here https://eservices.archives.gov/orde...rchives.gov&SWEFullRefresh=1&SWEFullRefresh=1, establish an account and request the records for his unit. They will let you know what they have and the cost for reprinting it, generally
$0.75 per page.