I've obtained a 50m range with -6dBm Tx power , and a simple superregen receiver, sensitivity -97dBm in open air using loaded 1/4 wave whip antennas about 8cm long.
As noted above, I get better than 300 meters line of site with two balanced dipoles and a superregenerative receiver. The same setup with just 1/4 wave whips gives 50 or so meters.
Radiation efficiency calculations for the 1/4 wave whip assume an effective ground plane, and in the real world (i.e. the hobby bench or a model), there is seldom a reasonable or effective ground plane adjacent and perpendicular to the antenna.
Poor ground plane performance is often the cause of low range or outright failure of hobby radio projects.