We use it on the farm to blow up stumps and yes, it's easy to buy. It is used often in rural areas like mine for this purpose and we buy it from one of the local gun shops. We blew up a stump that was 500 feet from the house and pieces of stump landed on our roof. It is activated by shooting it with a rifle. It is relatively safe, compared to dynamite anyway, which is what rural farmers used in the past to blow up stumps. Here is a short YouTube video of our stump blowing up.
Stump Removal