Locate images or a toy version of an AK-47 to create your model from. It is best to have several views, from different angles to get the details right. Print out at least one side profile view at full size, about 34-1/2 inches long. This can be done by using a "poster print" mode on a computer to create a multi-page image that can be fit together, or by having it done at a copy or print shop. Cut the image out and tape it to your cardboard.
Cut the cardboard with a craft knife, following the outline of the image. Cut five of these, from standard 1/4-inch corrugated cardboard and paste three of them together with white school glue, weighing them down with heavy books. Allow the pieces to dry for two hours.
Cut the barrel, pistol grip handle, curved clip and a strip 1/2-inch high from the top of the cartridge magazine section, which is the metal part in front of the rifle stock, from the remaining two cardboard cutouts. Cut a slot in one, the size and shape of the cartridge eject, on the right side of the weapon. Trim 1/4-inch from the top and bottom angle lines of the rifle stock as well. Paste these pieces to the outside of the cardboard rifle core you glued together. This will give the gun a bit of three dimensionality.
Wrap the entire gun in flat black cloth duct tape or black cammo tape to create more rounded edges for the barrel and stock and to make the gun more rugged.