How do I unlock this weapon?

Engineer

An Engineer's primary weapons are sub machine guns equipped with silencers. Most of these weapons have a low damage output but a very high rate of fire and exceptional close-quarters accuracy.

9A91 Avtomat

Unlock: Starting Engineer weapon

Details: With rather hard-to-use iron sights and effectiveness that is limited to close-range combat, the 9A91 is not among the best weapons, let alone the best starting weapons. Although it's hard to use in any situation other than close-quarters, its fast firing but low damage can take out enemies really quickly. It can be really useful (as well as other SMGs) when advancing in a building. The true flaw of the 9A91 is that it only has 20 bullets per magazine, and with a fast fire rate, you will have to really watch your shots or you will find yourself in a sticky situation that requires you to reload when close to enemies. With practice however, one can use the 9A91 firing in single shots for medium range kills.

SCAR-L Carbine

Unlock: 2,500 Engineer Points

Details: The SCAR is very similar to the 9A91 in the sense that they both have similar fire rates and damage, but the iron sights are much better and although the stats show similar accuracy, you can really be more effective with sight aiming. It also has a 30 bullet magazine which really is useful as the extra 10 bullets can save your life.

XM8 Compact

Unlock: 6,500 Engineer Points

Details:

The XM8 Compact is the sub-machine gun variant of the XM8 Prototype. It is slightly less accurate than the SCAR and 9A91 but does slightly more damage and has a faster rate of fire. It's iron sights are the same as the XM8 Prototype for the Assault Class and with burst firing it can be used effectively at medium-long range.

AKS-74U Krinkov

Unlock: 16,000 Engineer Points/Limited Edition

Details: The AKS-74U is an excellent SMG that has high accuracy and high damage, as well as high rate of fire compared to other SMGs. It's a definite upgrade from previous Engineer weapon unlocks. In simple bursts, it can take out enemies really quick, and from close-medium ranges too. However, it's advised not to hold down the trigger till the magazine is drained because like the AEK-971 for the Assault class, it has high recoil, so spraying will cause your crosshairs to move apart very quickly, or cause your sights to shift upward quickly.

Uzi

Unlock: 26,000 Engineer Points

Details: The Uzi has great iron sights and its damage and accuracy is slightly higher than the PP-2000. It is often under-rated over other Engineer unlocks, it has a fast fire rate and is recoil is medicore. It is ideal to burst fire the weapon for medium-to-long range encounters.

PP-2000 Avtomat

Unlock: 32,000 Engineer Points

Details: The PP-2000 has a 40 bullet magazine and has a reload time of a pistol, but its ron sights are often difficult to use so while it's not recommended to be used at long range it can be in emergency's. It has the best accuracy of the SMG's, close to that of a sniper rifle and it's damage is only slightly lower than the UZi.

UMP-45

Unlock: 43,000 Engineer Points

Details: The UMP-45 has similar damage to the AK-74U and the same fire rate of the SCAR. It's downside is the small 25 round magazine and hefty recoil when fired full auto, causing your crosshairs and sights to go haywire.