|The following is based on S.T.A.L.K.E.R.: Shadow of Chernobyl cut content and has not been confirmed by canon sources.|
5.7x28mm FMJ is an unused ammo type which was partially included in S.T.A.L.K.E.R.: Shadow of Chernobyl.
A relatively new cartridge made for the FN P90 and the FN Five-seven pistol by FN Herstal. The 5.7x28mm is a middle ground between pistol cartridge, such as the 9x19mm used by the MP5 and intermediate assault rifle rounds, such as the 5.45x39mm, used by the AKS-74u. Though never displacing pistol rounds as the ammunition of choice for sub-machine guns, it has gained a reputation as a powerful armor defeating round that will not overpenetrate. This has lead to the adoption of the round for special forces in hostage rescue or CQC situations.
No weapons implemented in the S.T.A.L.K.E.R. games accept this ammunition. However, it can be assumed that the unimplemented FN P90 would have used this ammunition.
5.7x28mm FMJ rounds are present in Build 1935's resources, complete with inventory icons and an in-game model. However, the ammunition is not carried by any Stalkers and is not available for trade.
Shadow of ChernobylEdit
Unlike Build 1935, Shadow of Chernobyl does not include inventory icons for this ammunition. The in-game model remains present and the ammunition is still implemented within the game's code. Curiously, the ammunition appears to have stats identical to those of 5.56x45mm SS109 ammunition.
Shadow of Chernobyl specifies another 5.7x28mm ammo type: 5.7x28mm AP. However, in real-world terms the Full Metal Jacketed variant of 5.7x28mm ammo is the Armor Piercing variety. 5.7x28mm FMJ rounds are likely meant to represent some other, non-armor piercing variety of round, such as Jacketed Hollow-Point or Sporting rounds.