Hey, I've recently bought Fallout: New Vegas on my http://steamcommunity.com/id/sgtnapalm in the Quakecon bundle. (This is not my first playthrough, however.)

I've decided to play an unarmed build, and of course that means that I would be getting the Ranger Takedown for myself.

But, it seems to be bugged. Occasionally when I use it, it works 100% of the time, and it knocks everybody over.
Sometimes, it just... dpoesn't.
To illustrate what I mean, I recorded http://www.youtube.com/watch?v=-Pp13Q52U6M.

Now, I can't tell what's supposed to be happening here because my Google powers could not find me a clear answer. Is it a bug? Is it supposed to be this way?

Any help would be greatly appreciated.

Ranger Takedown works.....in 3rd person.

In 1st person you simply do a palm strike.

Watch the video. I do it both in 1st and 3rd person, and the animation plays.
But it has absolutely no effect on any of the targets, even while using a myriad of unarmed weapons.

To reiterate Ranger Takedown does not do its intended animation in first person.

But if you want greater effectiveness first hold the attack button THEN hold back.

Alright, first take a look at this video. It is a different video.
http://www.youtube.com/watch?v=UWUqKcqZ-dE

Notice how when the person executes the attack, the target becomes limp, turns into a ragdoll, and falls to the ground.

Now, look at my video.
http://www.youtube.com/watch?v=-Pp13Q52U6M
Notice how when I execute the move, (REGARDLESS OF FIRST OR THIRD PEROSN) the target does not become limp, does not turn into a ragdoll, and does not fall to the ground. (Enemy death notwithstanding.)
If you pay further attention you will notice that each and every one of my attacks are, in fact, landing. The target recieves damage, the target is pushed back slightly, yet that is the extend of the damage caused by the attack.

The question I'm asking is: Why does this happen?

In regards to the second part of your post: In my experiments, this does not make any difference. And as far as I can tell by looking at example videos, distance does not matter, as long as the actual attack reaches the opponent.

Well Cliff tripped at the end of the video but boy that Novac Settler has adamantium bones.

Best conclusion I can come up with? Series of unfortunate events. Keep trying.

Sorry.