A shortened version of the British Boys anti‑tank rifle was deployed in 1942 for issue to airborne forces. This variant had a 30‑inch (762 mm) barrel instead of the standard 36 inch (910 mm) model, which reduced its muzzle velocity and overall effectiveness . The shorter barrel also made the weapon heavier and more unwieldy to carry, especially in the demanding conditions of airborne operations
MK1
W Mark 1 a 60 g (930 gr) AP projectile fired at 747 m/s (2,450 ft/s), and the W Mark 2 ammunition, 47.6 g (735 gr) AP at 884 m/s (2,900 ft/s). The W Mark 1 could penetrate 0.91 in (23.2 mm) of armour at 100 yards (91 m)
Mark 2, which fired a tungsten-cored projectile at 945 m/s (3,100 ft/s). The Boys’ effective range against unarmoured targets (for example, infantry), was much greater. This load proved capable of penetrating 20mm of armor plate at 300 yards.
MK2
The Mark 2 was a shortened, lightweight version intended for use with airborne troops, but it was just as ballistically ineffective as its predecessors, and the recoil was even more brutal than the full-size model. A taper (or squeeze) bore barrel was tried to increase muzzle velocity in the same manner that the Littlejohn Adapter tried to extend the useful life of the 2-pounder gun, and experiments were also conducted with the .55-caliber cartridge casing necked down to fire a .303 bullet at extremely high velocity. However, by that time the Boys was already being retired.
The para model is a shorter lighter model that failed due to lack of power. the mk2 is an improved model with more power than the original gun. The MK2 had nearly the same penetration at three times the range. I am going with the MK2 not being a para model as the mk2 has been multiple times been referred to as a stroner gun. did they make the para then a cut down bullet that made it better. i could use some help on this before i post suggesting any boys gun.