Where the built-in engine runs out
Roblox's physics engine is a capable general-purpose solver, and general purpose is exactly the limitation. It does not model tyre slip, it does not distinguish a projectile from a thrown brick, and it makes no promises about determinism, which means the same inputs on two machines can produce different outcomes.
For most experiences that is fine. For vehicle simulation and any game where a shot either hit or did not, it is not. Physics-7 extends the platform's solver with domain-specific systems that are deterministic and authoritative on the server.
Vehicles that behave like vehicles
Vehicle dynamics are modelled through the suspension and the contact patch rather than by applying forces to a chassis. Each wheel has real travel, spring and damper characteristics, and generates lateral and longitudinal force based on slip. Weight transfer under braking, cornering and acceleration emerges from the geometry rather than being faked.
This is what makes a vehicle feel like it has mass. Understeer, oversteer and loss of traction on a poor surface are consequences of the model rather than special cases someone had to write, which means they behave correctly in situations nobody specifically tested.
Ballistics and determinism
Projectiles are simulated with drag, gravity and, where it matters, wind. They travel over time rather than instantly, so leading a moving target is a real skill and distance genuinely affects difficulty. Impacts are resolved against the same authoritative state on every machine.
Determinism is what makes this defensible. The server holds the authoritative simulation, clients predict locally for responsiveness, and predictions are reconciled against server truth. A client cannot manufacture a hit that the server does not agree with, which is the property that makes competitive play viable.
Destruction within a budget
Environmental destruction and debris are handled through a managed pool with an explicit budget. Fragments are pooled and retired, distant debris simplifies or disappears, and the system degrades gracefully under load rather than dropping the frame rate at the worst possible moment.
Collision handling uses spatial partitioning and simplified proxies so that the expensive precise tests only run where they matter. The aim throughout is that simulation quality scales with what the player is looking at, not with what exists in the world.