House Oversight Committee Chairman Rep. Darrell Issa, R-Calif. during a hearing on Capitol Hill in Washington. (J. Scott Applewhite/AP)

Officials at the Department of Homeland Security denied Thursday that its large-scale ammunition purchases were an effort to keep bullets out of the hands of private citizens.

At a hearing on Capitol Hill Thursday, top DHS training officer Humberto Medina said he could "say categorically that was not a factor at all" in the purchases. He also noted that ammunition DHS purchased would be used for both operations and training purchases.

The Associated Press reported in February that DHS was planning to buy more than 1.6 billion rounds over the next five years, a number that sparked fears of government stockpiling – which DHS previously denied to Whispers. Officials told lawmakers DHS actually was planning to buy only up to 750 million rounds.

But Rep. Darrell Issa, R-Calif., said it still looked like the government was unnecessarily amassing ammunition.

"The idea that you have to have excess rounds, year after year, flies in the face of common sense," Issa said. Medina argued that DHS keeps a reserve of ammunition because of market fluctuations and because of past problems with vendors.

In fiscal year 2012, DHS purchased more than 103 million rounds of ammunition, to be used by about 70,000 DHS officers who are currently authorized to use weapons. Rep. Jason Chaffetz, R-Utah, said Thursday that "the math" didn't make sense, pointing out that this means an average 1300-1600 rounds per DHS officer – some 1000 rounds more than the average for an officer in the Army.

DHS agents and officers need extensive training because they are "exposed to a variety of situations" and "only have that weapon to protect their lives," Medina said. "They can't contact air support [like an officer in an army could.] They have to be proficient at a very high level."