If the barrel and lug are forged as one, that is a chopper lump (demi-bloc).

This is a mono-bloc. (Pieper 1881)


http://www.google.com/patents/about?id=QiBMAAAAEBAJ&dq=246195

The Stevens catalog above clearly shows a chopper lump. The lump is forged as part of the barrel. Beretta still uses the monobloc.

(Beretta 1938 catalog)







Pete