Well quoted by Wikipedia -
The Remington 1100 is a gas-operated semi-automatic shotgun, popular among sportsmen. The Remington 1100 was the first semiautomatic shotgun to feature significant reduction in felt recoil, light weight and reliability.
Designed by Wayne Leek and Robert P Kelley,[1] the Remington Model 1100 was introduced in 1963 as a successor to the Model 58 and 878 gas operated shotguns. The Model 58s had supplanted the recoil operated Model 11-48, which retained the long recoil action of John Browning's original design, present in the Remington Model 11 and the Auto-5. All models of the 1100 are gas operated with a mechanism that noticeably reduces recoil.[1] Several variations of the Model 1100, in 12, 20, and 28 gauges, and .410 bore are still in production as of 2012. The Remington Model 1100 ushered in the era of successful and reliable gas-actuated autoloading shotguns, and it is the best selling autoloading shotgun in U.S. history.[1] with over 4 million produced. The model 1100 holds the record for the most shells fired out of an autoloading shotgun without malfunction, cleaning or parts breakage with a record of over 24,000 rounds. The record was set in 1978 with a Remington model 1100 LT-20. Breaking this record has been attempted with several other models of Semi auto shotguns but has yet to be broken. In 2011 Remington introduced the model 1100 Competition Synthetic, showing the 1100 still has a lot of life left in it.