The C-17 does not use 3rd party cargo handling systems. The C-17 cargo handling systems and air drop systems were all designed in-house by Douglas Aircraft and were fully integrated into the C-17's cargo floor and loadmaster stations. There are 18 463L pallet positions in the C-17 and all the pallet locks are electrically operated and can be released individually or in groups, including releasing them all in a "gang release".
I know Airbus folks looked at the C-17 cargo handling systems and considered a similar system on the A400M. But I understand (but cannot confirm) that they decided this was too expensive and went with 3rd party systems similar to the C-130, which each service had to buy on their own, separate from the aircraft.
For a C-17 "combat offload", the pilots do an assault landing which minimizes the landing rollout and then they back taxi to the approach end of the runway by backing up under aircaft power using thrust reversers. While backing, the cargo door is opened and the ramp lowered to the level position. When they get back to the other end of the runway they stop, hold brakes, run up the engines to high power, the pallet locks are released, the brakes are released, and after the last pallet drops clear, the ramp and door are closed while simultaneously increasing power to max and they accelerate and take off again. The entire evolution from initial touch down to back in the air can be done in as little as two minutes, theoretically less time that it takes the bad guys to spot the plane and get mortar rounds on target. Of course this means the guys on the ground have to dodge mortar rounds while they are unloading/moving up to 18 pallets of stuff.
Since the C-17 can deliver up to 18 pallets at up to 10,000 lbs each in this manner, there is "usually" no need for another delivery for awhile, so having the runway tied up with cargo should (theoretically) not be a problem. But this is not always the case and it was not the case in Afghanistan and in Iraq on a number occasions. If the runway is long enough, a different but similar tactic is used. In this case the aircraft lands upwind as usual and does a high speed taxi to the other end of the runway. At the other end the C-17 does a quick turn around (C-17 can turn around on a 90 foot wide runway under its own power) and then does a combat offload at that end, but this time accelerates and does a downwind takeoff going back out the way it came in. Since its taking off very light it can usually be done with little runway even going downwind. With a long runway (6000 ft or longer) up to four C-17 loads (72 pallets!) can be offloaded very quickly in this manner. More typically, two loads of vehicles are quickly driven off and then two loads of pallets are combat offloaded. A complete Marine LAV Company (LAV=Light Armored Vehicle, based on the 8x8 MOWAG Pirhana) was delivered this way into Afghanistan.
Here's a video of a C-17 combat offload of 16 pallets:
https://www.youtube.com/watch?v=AJt97q49GRU