In 1987, the new gas compensated Model 11-87 was introduced. While he Model 1100 and the Model 11-87 are similar in design, there are a number of differences which will not allow parts to interchange.
The biggest difference is that barrels are not interchangeable between these models.
- The Model 11-87 also has a slightly longer barrel extension. (This is the part that connects directly into the receiver)
- The gas cylinders are welded in slightly different locations. This is partly because the Model 11-87 has a longer magazine tube.
- The Model 11-87 has 2 gas orifice holes. Only the 2-3/4 inch chambered version of the Model 1100 will have two gas orifice holes while the magnum Model 1100 barrel has only one.
Another difference is in the interchangeability of shotshell lengths.
- The Model 1100 can shoot only 2 3/4" or 3" shells depending on the barrel installed. (Always check your barrel for the proper type of ammunition to shoot in it)
- Model 11-87 models with magnum barrels can shoot both 2 3/4" and 3" shells interchangeably. To accomplish this, two additional holes are drilled in the top/front of the gas cylinder, and covered with a tempered steel spring. There is a relief cut made into the gas cylinder to accommodate the spring. The Model 1100 gas cylinder will not have the relief cut or the spring.