I have heard the subject of the composition and weight of Gutt's sword on other websites and this one, people have even said that Iron is so heavy and it would weigh up to 800 pounds, well to clear things up for you (in case you didn't know) that even the finest swords forged like Katanas for example are forged from IRON, like the Dragonslayer, Godo said that he forged it from Iron, it could be steel, because steel is just Iron with no oxygen and the right amount of Carbon (Carbon may vary, higher or lower amounts are added depending on the type of metal you want, e.g. hard, soft, stronest, weakest). Steel can be produced by folding and hammering out the air of a SLAB of iron, or you can use the Bessemer process to heat the metal to super high temperatures to remove the oxygen (something that wasn't invented until 1855). So now some people might want to reconfigure your idea of how heavy the Dragonslayer, even though the thing is still damn heavy.