Weapon Name- HK Mp8
Round Type- 5.7mm x 28mm
Over-all length- 415 mm (16.3 in) stock collapsed/ 638 mm (25.1 in) stock extended
Barrel length- 180 mm (7.1 in)
Weight- 1.9 kg (4.19 lb) without magazine
Rate of Fire- 950 rounds/min
Feed Mechanism- Detachable Box Magazine
Round Capacity- 20, 30, 40
Effective Range- 200 meters
Range- 1800 meters (400 for kill)
Accuracy- 2 MOA
Accessories- Picanty Rail
Quick switch firing mechanism- N/A
Scope/Sights- Picanty Rail
Muzzle Velocity- 715 m/s
Firing System- MP7
Miscellaneous/electronic information- Essentially an MP7 refitted to fire 5.7mm x 28mm rounds
Basic Information
The weapon is essentially an MP7 that fires 5.7mm x 28mm rounds. One might ask why this change was made at all- seeing as how they have nearly identical ballistics, the same level of accuracy, roughly the same weight, roughly the same recoil, are roughly the same size, and roughly the same ability as armor penetration. The reason for change, however, is a very obvious one when the facts are considered. While the both are similar in terms of ballistics (projectile flight path), the 5.7mm achieves better long range ballistics then the 4.6mm rounds (when comparing their base rounds). While both achieve roughly the same velocity, the 5.7mm achieves the 715 m/s velocity with a 2.0 gram round while the 4.6mm achieves the velocity with a 1.6 gram round. While in terms of penetration and damage after penetration they are roughly equal (as the high velocity on a smaller diameter reaches the same pressure levels as the 5.7mm) the amount of kinetic energy transfer is rather substantial. While the 4.6mm only drops 100 joules in comparison to the 5.7mm, due to their low kinetic energy to begin with, this ends up being that the 5.7mm round has a 21% energy increase over the 4.6mm. In comparison, this would be roughly the energy difference between a 5.56mm round being fired from a 20 inch barrel and a 6.8mm remington being fired from a 16 inch barrel (or the power of a 6.8mm remington carbine compared to a full fledged M16 or other type of primary service rifle).
This energy change serves as to the reason why the round is better; but it is felt, not heard. The round achieves again, better terminal ballistics, a 27% increase in over-all permanent damage, and is slightly more accurate. As well, due to the fact that the round requires more so on momentum than velocity than the 4.6mm round, the round sustains it's energy longer than a 4.6mm round, and also does not wear out the barrel as quickly (with a small round imparting a lot of friction on a short barrel comparatively with the 4.6mm). The 5.7mm also preforms better from a smaller package than a 4.6mm, which again is heavily velocity dependent. On the rounds which aren't velocity dependent in the 4.6mm, they lack a great deal of velocity, and as such are substantially less accurate.
All in all, despite the best performance by the 4.6mm, and it's ability to match and even exceed certain aspects of the 5.7mm round, the 5.7mm rounds sheer energy increase means that it usually results in better over-all performance than the 4.6mm, which is why it is the round of choice for this weapon.
