Right away! How about FQE? I love that gun on her. It just feels right.
Or, maybe more beginner-friendly, human soldier double tap build is pretty straightforward.
I actually agree with catastrophy. I think I have my share of experience with the Raider, and I totally HATE when I get 3 or 4 shots out of it.
Rhythm is actually a very important thing, even though it sometimes is overlooked because it's not something you have to actively think about. Rhythm is the ability to know how long it will take till you have a fresh mag and can start shooting again. It is what enables you to understand if it's better to take soft cover or if you can get away with just staying in the open and mowing enemies down. It's the thing that allows you to make decisions, knowing how much time each of your actions will take. It's something quite subconscious usually, but is very important. Messing with that brings much worse consequences than the good you get out of +50% shots.
Most of the actions you (read: me, at least) take during the game are governed by muscle memory rather than completely conscious and reasoned decisions, and that's why something that messes with your habits messes up those actions as well, and that can have very bad consequences.
It is not that bad when you get a match when you can consistently get 3 shots out of her. Then after the first few waves you can kind of adapt your rhythm to that. But that's quite rare in my experience. Most of the times you get the 3rd shots like, once in 3-4 mag spent on average, and in a completely random and unpredictable way. This, is what I really hate. It takes my habits, my old and trustworthy rhythm and flushes it down the toilet. Result? I seem to make all kinds of bad decisions about where to go and when, and what to do in general, My reload cancels become very lacking, and I find myself in all kinds of unpleasant situations because of all that - resulting in me hitting the floor much more than I usually do. All that, to sometimes have +50% shots in my mag? Nah thanks, I'm good.
My rhythm is fine whether my Raider has two shots or three--I mean, what is there to rhythm about anyways? A rhythmic difference between cloak-shoot-shoot-reloadcancel-shoot-shoot and cloak-shoot-shoot-shoot-reloadcancel-shoot-shoot-shoot is really easy to handle. It doesn't screw my muscle memory whatsoever.
I actually find it rather baffling that there are people like you that can't handle such things with ease. Genuinely surprised.
Anyways, as for the topic: Claymore is alright, but nothing is more satisfying than double/triple BANG BANG headshot with a Raider. Although with a Raider a Stability Mod is a must if you want to have respectable shooting range (you can shoot targets comfortably at one side of the pathway at Rio the from other side of the pathway, for instance)