The shooting range can be found in the sub and can be accessed after the 2nd mission. You need to score over 375 points on the range to get this achievement. It is fairly simple to do if you use the sub machine gun. Their is unlimited ammo to the right hand side of the range so you can try as many times as you like. It took me 3 times in total to get a score of 400 points.
I will leave a guide below on where to find the range and my example of getting the achievement.