I cannot assemble...how to assemble

[charlie hill]

I just got a parker double barrel shotgun from my wifes grandfather.
I have never had a double barrel before. (only a pump)

It is circa 1936.
Has no hammers.
Is 20 gauge.

Came in a case apart.

Ok,so I am able to put the barrel to the receiver no problem
I am able to put the forend on the barrel when it is not on the receiver.

I cannot get the whole package together.

If I put the barrel to the receiver I cannot get the forend on and visa versa.

I had thought you put the barrel to the receiver and then the forend to the barrel.

What am I doing wrong ?

Thanks
Charlie