Dear Captain Zimmerman (Ret),
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located a series titled Artillery Unit Records, ca. 1965 - ca. 1972 in the Records of the United States Forces in Southeast Asia, 1950-1975 (Record Group 472) that includes records of the 1/30 Artillery for 1968-1971 in Boxes 629-647. We also located a series titled Infantry Unit Records, 1965 - ca. 1973 that includes records of the 2/28 Infantry for 1965-1971 in Boxes 548-563. For access to these records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at firstname.lastname@example.org.
In addition, we searched the Catalog and located numerous records pertaining to Fire Support Bases (FSBs) in Vietnam. Please look through these prior to contacting RDT2. A brief description of FSBs is available from the Army War College at https://ahec.armywarcollege.edu/trail/Vietnam/index.cfm.
We hope this information is helpful. Best of luck with your research!