Can't get high enough bitrate even with maximum target settings.

[adasimone]

I created an animation in After Effects. The company using my animation is requiring a minimum bitrate of 15000k. The file must be an mp4. I am unable to get the bitrate above ~5300k. 

Here is what I've tried:
CBR and VBR 1 Pass with bitrate set to 50. 
Maximum render quality toggled on and off.
Rendering both from the AE composition and from an uncompressed AVI.
Rendering from AE in the animation codec and then converting. 

No matter what I do the bitrate is the same at ~5300k. I'm at a complete lost. 
Everytime the bitrate  

[DBowker3D]

I'm pretty sure this is a simple fix: Don't use Variable Bitrate. Switch to Constant Bitrate. I use that any time I'm sending files I know will be further compressed.

15,000k is actually kind of on the low side for a file destined to be further processed BTW. I usually pick 30,000k for that, which is closer tot eh final Blu-ray spec.