It would appear he did not serve in the army.

Document # 001. The Vicksburg Daily Whig

Monday, May 13th, 1861 A Terrible Accident

The Warren County – Vicksburg Public Library, Vicksburg, Warren County, Mississippi

A terrible Accident – Austin Bobb - A B Reading & Company; A Cannon having been cast at the Foundry of A B Reading & Company, in this City, was this morning tested, when it exploded, crating sad havoc among the operators. One man by the name of Austin Bobb had his face to frightfully shattered this his recovery is considered impossible. Another man by the name of Dennis Scheme had his arm blown off, and sustained other serious injury. We have not learned whether his injuries are supposed to be fatal or not.
http://mv.ancestry.com/viewer/483a2225-0522-44b6-9933-6cb48ff6f3d9/15308657/245019011

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Name: Austin Bobb
State: MS
County: Warren County
Township: City of Vicksburg
Year: 1860
Record Type: Federal Population Schedule
Page: 964
Database: MS 1860 Federal Census Index

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Austin Bobb
in the 1860 United States Federal Census
Name: Austin Bobb
Age: 25
Birth Year: abt 1835
Gender: Male
Birth Place: Mississippi
Home in 1860: Vicksburg, Warren, Mississippi
Post Office: Vicksburg
Household Members:
Name Age
Austin Bobb 25
Mary Bobb 30
Jas Lowder 34
Martha Lowder 42
Mary A Lowder 13
Robt Miller 25

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There is a Funeral Record Austin Bobb 1836-1861

I have requested additional information at Ancestry.com