If you are using the rapidfire customization software, I'm coming up with 10.60 shots-per-second for the MK14 if your connection is good.
The P99 is significantly faster, I'll post that speed later tonight.
I'll also be adding these speeds to the "pre tuned" list and releasing an update rapidfire customization software, though any more due to connection/lag affecting rapidfire performance, I am now suggesting that people also try out the custom speeds. Pre-tuned speeds are really set up if you have a stellar connection. Start with around 10.00 sps, if it's not laggy/skippy, you can try increasing it - if it is laggy/skippy, try decreasing it.
(As always make sure your NAT type is OPEN and you use a WIRED internet connection to your console when possible. Many consumer wifi setups are known to have dropped packet issues, ESPECIALLY if you live in an apartment complex, duplex housing, in the city where lot sizes are small, etc. I had all sorts of problems with my WiFi to my XBOX360 when I lived in the city, and literally saw an improvement in gameplay when I went wired ethernet instead of using the wireless)