You might have to use trial and error to find the right mould. Sometimes it cannot be avoided, but I try to avoid mould seams anywhere that is going to be a beast to clean up later. From your picture above I cannot tell if the casing is closed at the bottom... if so I would make the bullet out of 3 parts, a nose that sticks into the cylinder on the top and the bottom ring sticking into the cylinder the same way from the bottom. the nose and the butt are relatively easy to mould and cast... as for the cylinder I would try the following...
I would try a 2 part mould by filling the cylinder center with silicone first. Make it a bit longer than your casing on both the top and the bottom and give it a fairly good locking texture at the bottom so that you can set it inside the second part of the mould without any wobbling. You might want to taper it a very little bit so that it is easier to connect the two mould parts. You can "extend" your center mould on the top/bottom with any wide tape. You also might want to use tape to cover the entire inside wall of your casing and get rid of any relief on the inside... that will make it easier to pull the silicone out later. It might require a bit of fiddling, but you should also be able to get away with placing your main pouring channel for resin in the center silicone part as well.
Once you have the center part of your mould finished, build a cage to contain the outer silicone. I use LEGO for this because you are very flexible in terms of size and form and they are re-usable. Take the tape off the bottom side of the mould, I would leave it on the top side to serve as the escape channel for the resin, make sure that the tape is thick enough for this purpose. Once you have the cage finished, use talcum powder to dust up everything and pour the outside part of the mould.
When your cast is cured, you should be able to pull the cast with the center mould out and then pull the main pouring channel out from the center like a sword from a sheath, that should also make it easier to then remove the center silicone from the cast by pushing gently on one side and pulling from the other.
I hope that helps and my description is understandable.