[M1 slug barrel on an M2 compact]

Thank you for your response.  The barrel does not seat flush with the receiver.  In the two attached photos, the shot barrel fits flush to the receiver, while the slug barrel does not.  Both appear to have the exact dimensions and design into the receiver.

[M1 slug barrel on an M2 compact]

Will an M1 slug barrel fit with an M2 Field using the modified forend?  The one I purchased (original Benelli) seems to be about 1/4 inch longer and does not seat as flush as the original shot barrel.