The masked gang broke into Michael Spiers shop in Taunton on 2 March, leaving two staff members traumatised.
The men, from London, were jailed for a total of 23 years at Taunton Crown Court after admitting robbery.
The raid culminated in an 80-mile police pursuit that ended with the robbers jumping into a river.
Reece Francis, 24, Louis Kelly, 35, Steven Shields, 32, all from London, and Charles Johnstone, 27, of no fixed address, were sentenced on Friday.
Three of the men received six-year sentences and the other five years.
Recorder Peter Towler said it had been "sophisticated" and "well organised", but there was no physical violence.
The court heard how the robbers threatened two men from an adjoining shop who tried to intervene, before driving off up the M5 and M4.
The police pursuit ended near Swindon, when the men crashed their vehicle before running across fields into a river.
Four men who smashed their way into a jewellery shop and stole watches worth £13,500 have been jailed for a total of 23 years.