You can use standard "duplex" reticles, which means that the indside of the cross hairs are much thinner than the outside part of the cross hairs.
You can also look at mil-dot reticles, which means that there are small dots on the cross hairs. With these reticles, you can take out some of the guess-work for the trajectory. However, you really don't need these reticles if you will only be shooting at a constant distance.
Zachary