From Valve Developer Community
$scaleonly affects model files that come after it in the QC. Specify it before any file references!
$scalealso accepts negative values. This can be used to flip/mirror animations or models if the compiled model is then decompiled. Note that the model's normals will be inverted and will be rotated 180 degrees backwards, this can be easily fixed in a Source engine compatible model editor.
$scaleprevents flex animation from working when using the VTA format. This limitation can be bypassed by using the DMX format.
$modelname "weapons/shell.mdl" $cdmaterials "models/weapons/" $scale 3 // before any SMDs$body shell "shell_ref.smd" $sequence idle "shell_idle.smd"