Kenworth -
The Long.
I'd be lucky if I'm able to nail anyone consistently inside the 200ft range. Even with heavier BBs (.28s or .30s), airsoft is just not meant for accurate target acquisition and neutralization. Also, given the FPS limitations of most fields, it's very rare that I swap/upgrade with internals that'll allow for maximum effective range engagements (550fps). She currently shoots under 430fps at the moment.
The Short.
Depending on windage, elevation and clear line of sight, between 130ft - 150ft