#4.3mm

Up to this point we’ve looked at calibers ranging from 5.56mm to 7.62mm, but today we’re going to look at something smaller… A lot smaller. The smallest caliber size that is feasible for a given current barrelmaking and projectile manufacture technology is .173″/4.32mm, and a natural centerfire platform for that caliber is the common 5.56mm case. This has led to a large number of cartridge types developed  – including the privately designed .17 Remington, and the German 4.3x45mm DAG – that are essentially similar, and so we will cover them under one umbrella here. Representative of this type in a military context is the Frankford Arsenal’s 4.32x45mm, which was loaded with a relatively low drag 27 grain full metal jacket projectile which – like the 5.56x38mm FABRL covered recently – possessed approximately the same ballistic coefficient as the 5.56mm 55gr M193 projectile. This means the 4.32x45mm Frankford represents essentially an alternate approach to duplicating the M193 round in a lighter package, by reducing the caliber instead of making the projectile lighter and longer.