New person to solid works needing help

As the topic says i am a new person needing help with solid works.

I have only been using it for a day or so and i got a grasp of the basics now and thought i would try and model something kinda simle that i thought i could do.

So i grabbed the thing closest to me and it happened to be the firing bolt out of my paintball marker.

Anyway i got what i consider something pretty good after a few hr's and was pretty happy with my first modeling attempt.

But there is one thing left to do and i can not for the life of me work it out.

I need to make an elliptical type shape dent in the side of it. I need it to gradually get deeper as it goes backwards along the bolt.

Any help[ with this would be great. If there is a tutorial that you know of that you could point me to or explain to me how to do it would be fantastic.

I have added a pic to try and show you what i mean.

I'd try and revolve a surface with the shape that you want, then cut the solid with the surface.

Exactly what I was thinking... or just do a revolve cut. Establishing the axis could be tricky, though.

You could also try a filled surface. Make a sketch tangent to the face of the cylinder and draw the of the elipse. Next, on a perpendicular plane, add a sketch point to guide how deep the cut should go into the part; then do a surface cut. Check out the SUFRACES tutorial on the SW help menu for more info.

Or mabye an INDENT feature could work?

Try sweeping an eliptical cut along an eliptical path.