From Halopedia, the Halo wiki
The Misriah Munitions Training Range was a firing range owned by Misriah Armory. It is located in Eos Chasma on the planet Mars.
Gregory Ramos, Michael Horrigan, and Alistair Estrin as part of Locke's team were at the range in 2555.
Michael Horrigan at the range with a magnum.
Alistair Estrin at the range with a Misriah logo in the background.