As the title says. When i got a new barrel and i release the bolt the cocking lever does not go all the way forward and the hammer is not cocked. Plus it takes quite an effort to pull it back the first bit. Its like its jamming.

1100 barrels are not 100% interchangeable.

The locking lug in the bolt is not fully seating in the locking cutout of the new barrel. Your locking lug may a bit on the plus side and the locking cutout on the barrel may be a bit on the minus side.

Check to see if there is a bur on the locking recess in the new barrel.

Check and see if there is a burr at the edge of the barrel extension that is preventing the barrel from fully seating.

Your hammer is cocked, it is just that the trigger is disconnected unless the bolt is all the way home.

Is your Remington 1100 20 ga. an L.W. model ? A regular 1100 20 ga barrel won t work.

No its an lt with a lt barrel