I made this for a gangster themed Halloween next week. All made from scrap cardboard, newspaper, string, hot and PVA glue. 

The stock & grips were traced from a picture then four copies were cut out of corrugated cardboard and glued together to get the required thickness and strength.

The main body is corrugated cardboard folded and taped into a rectangular box .

The barrel is single shets of newspaper, rolled up until the desired thickness is achieved and hot-glued into the body.  The detail on the barrel is made by winding thick string around in a spiral.

The muzzle was just a piece if cardboard wrapped around the barrel and glued and a sight added.

The rear sight is a flat 'U' of cardboard glued onto the main body.

The Bolt handle is a strip of newspaper rolled into a tight cylinder and glued in.

The Magazine is two circles of cardboard with a used 1/4in tape inner glued inside to get the thickness and cereal packet card glued around the perimeter

All of the pieces are then hot-glued together, the front grip has two plastic rods (from a coat hanger) glued on top and then glued into the main body for strength.  Where the front grip ends, there is a small - 1/4in - pad glued in place to keep the grip off the barrel

The whole thing is then covered in strips of newspaper covered in PVA glue and left to dry.

Once completely dry it was primed with aerosol grey primer then hand painted black and brown.  It has since had a few layers of aerosol clearcoat, which has made it far too shiny. Doh!