Spetznaz, Sukhoi
There is a long held view in India that the publicly stated range of the Brahmos is just to stay within the parameters of the MTCR, but the actual range may be close to double that.
As a co-developer of a missile, would the MTCR restrictions still apply?
Now, I really have no way of knowing whether or not the MTCR requirements have been applied to the letter. One would have to have clearance with the Indians and/or the Russians, and even then I doubt they would be willing to divulge that information.
With that said, I can obviously speculate. :) In my opinion, it would be really foolish for, say, the Pakistanis or the Indians to believe that the range of the BrahMos is what the Indians/Russians claim. I would bet that the actual range is longer than claimed, and may infact be usably longer than claimed. There are certain limitations though, such as the size of the missile and the fuel used that can be used to estimate maximum range, but I would be truly surprised if it was within the limits of the MTCR. Especially considering that the Indians co-developed the originally Russian missile.
It would also be advisable for possible targets of these missiles to recall the 1971 Operation Trident, where the Indian navy managed to pull off one of the most amazing naval operations in world history (and one that doesn't get its due in the international media). They pulled off an operation that was supposed to be, literally, impossible. For one the msisile boats used did not have sufficient range to get to target ...so the Indians simply had some ships tow the missile boats to where their range would suffice. Additionally, the Indian ships managed to use their anti-ship cruise missiles to attack Pakistani ships, as well as Pakistani land targets (the first use of ASCMs in the area, and the first use of ASCMs as land attack cruise missiles). Absolutely crippled the Pakistanis by taking out around 50% of their oil, taking out a lot of their ammunition (including attacking an American ship that was taking ammo to the Pakistanis), and absolutely crushing the morale in Pakistan.
Thus, I would be very sceptical that the range of the BrahMos has been limited to 300KM. I would bet that the actual range is more than that. Personally ...I would add almost another 200KM to that figure. :)