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The surface states of a topological insulator in a fine-tuned magnetic field are ideal candidates for realizing a topological metal which is protected against disorder.Its signatures are (1) a conductance plateau in long wires and (2) an always-increasing conductivity, and are independent of disorder strength and sample size.We numerically study how these transport signatures are affected by bulk physics in the interior of the topological insulator sample.We show that both signatures of the topological metal are robust against bulk effects.However the bulk does substantially accelerate the metals decay in a magnetic field and alter its response to surface disorder.When the disorder strength is tuned to resonance with the bulk band the conductivity follows the predictions of scaling theory, indicating that conduction is diffusive.At other disorder strengths scaling theory is systematically violated, signaling that scattering is reduced and the topological metal is not fully diffusive.