Hi Moocrew,
If I understand your question, the bulkhead does a lot more than just keep the "rocket out of the nose cone". That's not the job of a bulkhead at all really. Keeping the motor from moving forward inside the rocket is the purpose of the engine block, a ring or "donut" glued immediately above the engine which prevents the engine from moving but allows the ejection gases to pass through the hole.
A bulkhead is usually a solid ring or circle of thicker material to block the ejection gases. This can protect vital things on the other side of the bulkhead from the gases or, it can just be to reduce the internal volume the ejection charge has to pressurize. For example, if your rocket was 2" wide and 6ft tall, it might be hard to pressurize all six feet of 2 inch tubing. Putting a bulkhead at the 3 foot point means you only have to pressurize half the volume. Of course that means your rocket should seperate just below that, and below that is the parachute and wadding, then the engine retainer block, then the engine.
At the other end, to keep the motor from kicking out the rear when the ejection charge goes off, something has to "hold" it in the rocket. Friction fit works fine, especially for smaller motors, and is cheap and easy. It does have the drawback of needing to be just right though, too loose and it pops out anyway, too tight and it is a bear to get out afterwards. If you design the rocket so that the motor sticks out a ways, say 1/4 to 1/2 inch, it is relatively simple to grasp it with pliers and twist.
The most popular way to retain a single smaller moter is the classic engine hook. This premade flat spring metal piece allows the rocket engine to slip in easily but is retained positively. After the flight, you just bend it back out of the way and voila! Of course is springs back into place immediately for your next launch.
Other methods such as threaded rods with washers and nuts work better for large engines or multiple engines. The idea there is that the threaded rod is permanently inside the rocket. The engines fit with ease until you screw on the washer/nut and then the motors are "trapped". The washer/nut is sized to only cover the outside lip of the engine/engines, and not obstruct the nozzle in any way. After the flight, unscrew the nut and remove the old motors.
There are other ways as well. I recently built a rocket with a rubber band atached to an "L" shaped metal bracket to retain the motor. I needed to do that because my clearance was too limited to use a traditional hook. This allows the engine to move rearwards about a 1/4 to 1/3 inch, but still be held in, while it can be cocked sideways to get the motor in/out after recovery. I hope all this helps and is not too basic for what you were asking for.
If not, maybe someone else will find it usefull.
