GDG- Artillery at Gettysburg

[dwmadison at comcast.net]

I am currently reading "Contributions to a History of the Richmond Howitzer Battalion". In the second pamplet it states that at battle at Gettysburg they had fired much of their rifled ammunition and that many of the smoothbore guns had not been engaged at all.

My question is this. Is this true of just the Howitzer's not engaging all of guns in their battery or did the Confederates not use all of their available cannons during the battle. 

Dennis in Richmond