A jury at the High Court in Glasgow was shown CCTV footage of three masked men
carrying out the raid.
Alan Mitchell, 34, and Gary Mitchell, 20, deny robbing Eric N. Smith Jewellers in Ayr Road, Newton Mearns, on April 13, of a quantity of watches.
Prosecutor Sheena Fraser played a clip of the raid which started at 2.29.43pm and finished at 2.30.16pm with three men running out the shop.
Jewellery store owner Yvonne Smith, 52, said that up until then in had been an ordinary Saturday. She and her husband, five employees and some customers were in the store.
Mrs Smith said: "The first thing I was aware of was a really loud bang. It was like a gun going off. I ran towards where the noise was coming from.
"There were three men coming into the shop with masks and carrying a machete and two hammers. They kept shouting: 'Get back, get back.'"
She told the court the man armed with the machete stood guard over them while the other two smashed a display window of Rolex watches. The court was told these watches range in price from £3400 up to £50,000.The 38 Rolexes taken were worth £400,000.
The jury was shown CCTV which showed three masked men walking towards the shop and carrying a large piece of concrete. The concrete block was rammed in place to hold the front door open.
In court, Mrs Smith identified the defendants as the two men she saw in the shop.
The trial continues.