With the style having been decided the next step was to start looking for reference images of revolvers... specifically Colt .45 revolvers. I don't know why... I think I just like the name of the model and it's a classic.
So after searching high and low through the many sites I found a good collection of images. If you thought every revolver looked the same then you'll find that you were wrong. Sure the same features are there (barrel, hammer, cylinder, trigger) but its the finishing details such as the engraved patterns and embossed symbols which give each revolver a character of its own. This concept can be carried across to the modeling of the motorbike, which will help to make it seem even more like a one of a kind custom chopper.
Here are a few examples of the types of revolver I will be referring to when I go on to the design stage: