To unlock this achievement you will need 275 kills with the 1887 shotgun.
To buy the gun it will cost the user $50,000 ingame cash, As you continue to earn service stars for the gun you can unlock and purchase 2 mods they are sawed off stock and short barrel.
It's a nice overpowered 1 shot kill from close range, long range I wouldn't recommend at all so keep it for use on nice tight maps.
The 1887 shotgun is available for all classes, once purchased.