It's Not a Model Train, But....

[Sumpter250]

The turret works, too — though it doesn't fire (or at least we think it doesn't). But the two-foot-long barrel is motorized to simulate recoil, and it even has speakers that blare the satisfying, heavy noises treads make while crunching along.

The round for a 1/4 scale tiger would be close to 24 mm. a 20mm round could easily substitute for a "close enough for government work". That!, would make some noise!