I got a couple of rocket cartridges sitting around. The stuff you put under them model rockets and set with an electrical charge..
Man one time I took one of those things appart, and got all the black power into a bowl and lit on fire. It was cool. You might want to attach something like to your rocket for ultimate distance. Im sure u can devise a way of cutting the full pack to about 1/4 or 1/8 the size to give u a long enough burn to get some distance, and not enough of a burn to end up launching it for over a km.
The best is launching them cigar tubes.. When I was younger an older family friend use to launch them all the time. MAn those things were dangerous.