Incorrect.There is a set of o rings on the gas piston that have to be configured properly for the magnum 1100 shotguns to cycle light loads reliably. The owners manual has directions for configuring the o rings. Use a scribe to remove and replace the o rings or you will stretch them out.
There are no brass anything rings on an 1100. The first ones didn't have a rubber O ring but a steel 'V' ring. The piston and piston seal are both steel also. Stainless starting with the 11-87 in 1987.
I have swapped barrels about every way possible on 1100s. With a 2-3/4" barrel, a Magnum will reliably run everything down to 1 ounce loads. If you start shooting real heavy loads with the Magnum action sleeve, watch your buffer.
Funny, my 1100 had a rubber Oring, replaced with a Viton one, and two brass pieces making up the piston pieces - a nice 1100 in 28 gauge made in the 90s and if you didn't orient the piston rings right, your gun became a single shot-