S&B was founded in 1825, making it one of the world's oldest ammunition makers. (are there any older ones still in business actually?)
They make 2 million rounds of ammo daily, 66% of the production goes to civilian markets. 30% of production is sold in US.
I.e. S&B sells 219.000.000 rounds of ammo in US annually.
The explosion happened in the part of manufacture when the primer is inserted into the cartridge. The detonation was contained to the building where it happened with no damage/danger to anything around.