I have among various FN 5.7x28 rounds one with a black-painted tip. The headstamp is 5.7 x 28 FNB 00. I have it listed as an armour piercing round, but can find no mention of it in any of the listings of current or discontinued 5.7mm ammo.
Can anyone confirm that it is an AP (in which case I presume that it was only experimental?) and give me FN’s SS designation? Also, any details as to construction or performance?