While it seems like a lot, let’s do some math.
There are about 200,000 DHS employees. Using the same ratio of 70/30 as the military (nonshooters to shooters)that means we probably have 60,000 people who need to practice with firearms.
Lets presume range time of 2 hours a week, and an ammo expenditure of 150 rounds per hour. 2 hours is probably high, but stay with me on this.
So, 60,000x2hoursx52weeksx150rounds gives us a total annual ammo burn of about 936 million rounds. My numbers are probably a bit high, but it makes the 1.5 billion rounds look a bit more reasonable.
Your estimate of armed federal agents in civilian agencies is somewhat low.
The Government released their last offical estimate of armed agent numbers in 2008. It was higher than you expected. An unoffical estimate for 2012 gives 200,000-220,000 armed agents in over 30 different civilian agencies.
The ratio of authorized shooters in the FBI and Secret Service runs from 30% to 45% of the staff. Other departments have generally lower percentages of shooters.
Shooters do not get 2 hours per week of range time in most departments. That is a problem. Only a fraction of shooters maintain current qualification. The ones who do maintain proficiency use up about 250 rounds per quarter in practice sessions.
These kinds of rounds are not for practice. They are +p critical defense frangibles. They are for the express purpose of killing people.
Personally I hope they are practicing with them because in the event of conflict they will have developed such a flinch that everytime the dimwits fire off a round their eyes will close. Suits me.
That still doesn’t explain the need for more expensive hollow point for practice when FMJ would suffice.
Not to worry, for when the GW crowd finds out how much carbon this will spew into the atmosphere...