The European ballistic protection standard EN 1522 requires multiple tests. For example, to qualify for a FB5 rating the test frame must pass the FB5 test and all the lower ratings such as the FB1, FB2, FB3 and FB4 tests as stated in the EN 1522 standard.
The abbreviation "FB" is defined in the standard EN 1522 and is used to indicate the protection level of opaque (non-transparent) materials such as armor steel, which are often used in armored cars.
EN 1522 FB5 class requirements for testing with hand guns and rifles:
Type of Weapon
Test Range (m)
Bullet Velocity (m/s)
5.56 x 45*
* To achieve the stated values for [5.56 x 45], the recommended barrel twist length = (178± 10)mm
(a)FJ=Full steel jacket (plated)
PB pointed bullet
SCP1 soft core (lead) with steel penetrator (type SS109)
Note: When a shot is to be fired at a single point the test range may be reduced to achieve the firing accuracy as defined in Section 6 of EN 1523. In this case it may not be possible to measure the velocity of the bullet.
The armor steel and so on materials achieve ballistic testing to EN1522 FB5 class, meaning they are certified to withstand firepower from AK47s and other assault rifles.