The achievement requires you to get a Gold Service Star with the M1 Carbine. The first Gold Service Star for a weapon is earned at 275 kills with the weapon. The weapon was added as part of the 'Robbery' Title Update and costs $66,000 to buy. Like all WWII weapons in the game, it's very limited in attachments with only 3 attachments available.
The M1 Carbine is a single-shot weapon, which means that you have to pull the trigger every time you want to shoot. It has a fairly high damage output, with 3 or 4 body shots easily killing an enemy player. I suggest using this weapon on medium-sized maps like Hollywood Heights or Bank Job since it's stopping power isn't too big up close and bullets drop severely at long range.