My remington 1100 cycles two shells after i shoot my first?

Got a used, older 1100 that only takes 2 3/4 shells. Bought some winchester target loads to show my mom how to shoot a semi auto. I chamber one, have two in the tube. Ill shoot the first, then the next two jam up the ejection port. If I only have one in the magazine tube, it shoots and cycles fine. Buddy of mine had a semi auto awhile back and said something about different spacers for different shells, but I believe he had a browning. I have heard about issues with an O ring and 2 gas exhaust holes, but those generally make it not cycle at all instead of sending two in the receiver. Thanks for your time.