The Armored Personnel Carrier (APC) is a heavily armored vehicle. It can effectively shoot down most infantry without receiving significant damage, excluding rocket soldiers and shock troopers. For larger blobs, consider crushing instead (see below).
APC infiltration[]
The APC can be produced early in the game by soviets. A player can carry 5 rocket soldiers, grenadiers, or flamethrowers in an APC and infiltrate the enemy base, in an attempt to destroy some buildings. Harming the economy in the early game by destroying Ore Refineries or Ore Trucks can be fatal to the opponent on the long term, and since the APC and the above units can be produced early, this tactic can be employed early in the game.
APC scouting[]
The APC can also be used for scouting. While slower, pricier and having lower vision than ranger jeep, it can aggressive recon inside enemy base while sustaining small arms fire thanks to durable armour not present on its counterpart. On the other hand, it should be noted that a Tesla Coil leaves APC with only 5000 health, and driving through a concentration of tanks, rocket soldiers or turrets will stop these hollow steel bricks in their tracks.
Sometimes this tactic may be used to confuse and distract an opponent, because enemies have no way of telling apart an empty scout and an infiltration vehicle full to brim with demomen ready to take down a Construction Yard within seconds. That might lead the opponent to panic, and sending vast part of his force to destroy the decoy, allowing true APC attack to cripple the opponent with much less resistance.
Direct combat[]
While nowhere as cost-effective against enemy infantry as micro-managed Mobile Flak, APC can still spread death among enemy ranks lacking anti-armour weapons thanks to the heavy armour, but relatively high cost combined with mediocre firepower of APC's machine gun means that it takes quite a while to deal with multiple enemy soldiers, giving the opponent time to react.
One APC is more than a match for about 14 rifle infantrymen and 4 shock troopers, but as little as 3 rocket soldiers can overpower it.
For larger blobs, crushing enemies by manually driving over them is far more effective than shooting them. The APC's speed helps to crush several enemy infantrymen before getting destroyed. Multiple APCs can be used to maximize the effect.
APC, thanks to fairly tough armour, may also effectively counter wheeled recon vehicles, one of them overcoming two flaks or three rangers at a time. It might be also used to flank and destroy artillery or V2 from close distance. Any kind of tanks, even the lightest one, can tear multiple APCs to pieces though.