By garrisoning an Peacekeeper your turret will kill any basic infantry in less than one second. However, you can have another weapon by garrisoning an infantry inside it like the Multigunner IFV.
The standard weapon does a good damage against every unit, it kills Hammer Tanks in 12 seconds and a Peacekeeper or Flak Trooper in less than 2 seconds (2 volleys). As the Allies Construction Yard has a very large building radius, some players use it to put the Multigunner inside the enemy base, doing a lot of damage.
It can also be used to kill aircraft, but if you want to take down Vindicators you will need to have at least 3 turrets. It’s hard to evict them since they can be placed next to enemy units, doing a lot of damage until they get out of range. The famous instant pop-up turret is used to kill both infantry and tanks.
One of the most popular defenses in the game. In Allies or Soviets matches they are a must, they can provide a good defense or even be used in an attack force when turret crawling. Each faction has two defense turrets (3 for Soviets) that are used a lot on this game.