Just adding my opinion on this:
First of all, I love the guide, good job on it.
I am mainly a railgun user, even though I have every other weapon in the game m3, railgun remains my favorite.
One thing I'd like to point out, is that railgun is in fact good for capturing, on double damage you are able to one hit kill most opponents, giving them almost no time to damage you.
Also, railgun's slow firing rate is an advantage. Being able to hide behind walls and pop out occasionally to shoot your enemies while still keeping the same damage rate as if you were not hiding behind a wall is a very effective strategy. Think of it this way: The less times you have to pop out from behind that wall, the less times you will be shot by an enemy waiting for you

Good damage + Slow reload + Some skills = A very fun weapon.