Assault weapons with large capacity magazines are capable of spraying thousands of rounds a second.
First off male cats spray, NOT GUNS, water hoses spray, NOT GUNS, fear mongering anti-gunners spray out there asses, NOT GUNS. I know of no assault weapon that is used today that can put out thousands of rounds a second. The more bullets that a gun puts out per minute makes for less accuracy, a hand held weapon using full auto most times results in some loss of control of the weapon by the shooter and reduces the effectiveness if the weapon.
M-16a1 has a cycle rate of 650-750 rounds per-minute, this is dependent on a continuous feed of ammo, which the M-16a1 is not designed to do. One must manually replace each magazine with another taking up time. A best guestamate of the fire rate of a M-16a1 under ideal conditions and a real good shooter is about 300-400 rounds a minute. This is a far cry from the thousands of rounds a second that most fear mongering anti-gunners spray out there asses.
The Ingram M11 in 9mm has one of the highest cycle rates coming in at a rough 1200 rounds a minute. This again is calculated on a continuous feed of ammo, which this weapon is not designed to do either. A conservative estimate is around 500 rounds a minute due to the operator having to change magazines after every 30 rounds.
A good site on the cycle rates of deferent supposed assault weapons is here.
Just click on the weapon you wish to read about on the left of the page.