if you're going to attempt a model with splines, i really suggest doing things in different parts. especially the barrel, because it's a tapered cylinder, not a block. and you can replicate curves (like the trigger gaurd and grip) by clicking and dragging the cursor.
but you're getting the hang of it. keep it up! multiple chamfers don't hurt either

. oh, yeh, and someone may come in telling you to use plane modeling, but not tell you how to do it... so reinforce what you know is what i say.