First Sergeant Grundbacher enlisted in the Marine Corps in September 2002, and reported to Marine Corps Recruit Depot, San Diego, CA in April 2003. After completing recruit training and Marine Combat Training, he reported to the Marine Corps Cannon Crewman Basic Course at Fort Sill, Oklahoma and upon graduation was assigned the Military Occupational Specialty 0811.
Private First Class Grundbacher then reported to Golf Battery, 2nd Battalion 11th Marine Regiment, 1st Marine Division where he served as M198 Howitzer Cannon Crewman. In September 2004, Lance Corporal Grundbacher deployed to Ramadi, Iraq as provisional rifle company with Golf Battery in support of Operation Iraqi Freedom II. In June 2005 he was meritoriously promoted to the rank of Corporal.
In March 2006, Corporal Grundbacher deployed with Golf Battery to Fallujah, Iraq where he served as M198 Howitzer Section Chief in support of Operation Iraqi Freedom 5-7. In August 2006, he was promoted to the rank of Sergeant. In October 2007, Sergeant Grundbacher deployed with Golf Battery as M777A1 Howitzer Section Chief in support of Battalion Landing Team 1/5, 11th Marine Expeditionary Unit.
In January 2009, Sergeant Grundbacher reported to Drill Instructor School Marine Corps Recruit Depot San Diego, California and upon graduation reported to Golf Company, 2nd Recruit Training Battalion. During this time, he served as Drill Instructor and Senior Drill Instructor, and Senior Drill Instructor for Receiving Company. In December 2010, he was promoted to the rank of Staff Sergeant.
In March 2012, Staff Sergeant Grundbacher reported to 5th Battalion, 11th Marine Regiment, 1st Marine Division where he served as M142 HIMARS Launcher Chief. In July 2013, Staff Sergeant Grundbacher deployed with Quebec Battery to Afghanistan as Launcher Chief in support of Operation Enduring Freedom. Upon return Staff Sergeant Grundbacher assumed the role of Platoon Sergeant for 2nd Platoon, Quebec Battery.
In January 2016, Staff Sergeant Grundbacher received orders to Marine Corps Training Mission, United Arab Emirates. In July 2016, Staff Sergeant Grundbacher deployed to Dubai, United Arab Emirates where he served as Advisor/Trainer for the Logistics Battalion of the Khalifa Bin Zayed Brigade, Emirati Presidential Guard. In August 2016, he was promoted to his current rank of Gunnery Sergeant.
In May 2017, Gunnery Sergeant Grundbacher reported to The Basic School, Quantico, Virginia for assignment as Battery Gunnery Sergeant for Artillery Instructor Battery, Combat Instructor Battalion and Company First Sergeant for Alpha Company 1-20. In March of 2020 he was promoted to his current rank of First Sergeant.
In March of 2020, First Sergeant Grundbacher executed orders to Military Police Instruction Company, Marine Corps Detachment, Fort Leonard Wood, Missouri where he currently serves as Company First Sergeant.
His personal awards include the Navy and Marine Corps Commendation Medal (2nd award), Joint Service Achievement Medal, and Navy and Marine Corps Achievement Medal (2nd award).