Here's a 1920's era Remington Model 11, with the barrel cut down to 20" (it was longer, but had some damage to it), as well as a magazine tube extension to match the length of the barrel, which I believe may bring up the capacity to six or seven plus one.
The Remington Model 11 is a licensed clone of the Browning Auto-5, a long-recoil shotgun designed by John Moses Browning in 1898, and the first commercially successful automatic shotgun ever put to market, coming out in 1900. Long-recoil is a lot like short-recoil, only the barrel, as the name implies, recoils a much longer throw, the length of the entire cartridge, then a fraction of an inch more.
Here's some slow-motion footage showing the action cycling:
https://www.youtube.com/watch?v=LEoDnrtVp2cIt looks pretty slick when the entire barrel recoils together with the bolt carrier; the bolt unlocks from the barrel which then is returned forward with the bolt carrier pausing, and then shortly after the bolt carrier goes forward, picking up the next cartridge and locking into the barrel. It utilizes a tilting bolt which locks into the top of the barrel, and the recoil spring is situated inside of the stock, in a sort of angled recoil-buffer style setup.
The original Auto-5 had a magazine cutoff which would let you easily eject the shell in your chamber without loading the next one from your magazine, so if you needed to switch to a slug on the fly that was easy, this feature is missing on the Remington and Savage copies. It's worth noting that the velocity of the barrel depends some on the setup of the 'friction-rings' which are situated around the magazine tube, so if you're planning on shooting light loads, you need to take off the handguards and adjust the setup of the friction rings, likewise for heavy loads which otherwise may batter the stock. It's not entirely unusual to find a used Auto-5 or Model 11 with a damaged stock as a result, but it's easy to prevent.
