If you brought it to 1811 it still would have been invented in the same year (whatever that is, 1870 or something), but would have started being made in 1811 because people would have started to replicate it at an earlier time. Of course, this means that by the time the inventor was supposed to be inventing it, the invention that he was famous for would have already been made. So essentially, he is still the inventor because he brought the machine gun into existence, but it isn't necessary for him to invent it.
Same with the laptop. Except what use does a laptop have in an age before internet besides playing electronic solitaire?