I'm making my first model ever in C4D, but I've already hit a problem. The part of the gun that I've modeled so far (below) is the barrel. If you'll look at the actual gun picture, there's a triangular shape to help you aim. How would I create a shape like that in C4D, and how would I extrude it? The area of my model circled in red is where I want to put the triangular piece, and you'll notice the triangular piece circled in the original picture. Since this is my very first model, I would very much appreciate all the help I can get!!!
(I know there's a lot of detail I've missed on the barrel. I'm going to include it; I'm just getting used to the shapes first. But I need help with this now!)
My model (so far

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Original gun:
