The M40A3 was introduced in the DayZ 1.7.5 patch and is the second bolt action sniper in the game, firing the same mags as the M24. The performance of the M40A3 are the same as the M24, Though it has a more modern appearance.
The M40A3 can be fitted with the Mod:Ghillie Attachment attachment, making the weapon harder to see in tall grass.