Most sources says around 50Km and that's normal medium BVR range, similar to earlier Aim 120 (50 to 80Km), MICA (60 to 70Km), or SD 10A (70Km).
Which is what the ACIG article addresses: the range of the Derby has been portrayed as longer than it actually is. Look at it this way: considering it uses an Python rocket engine adapted for slower burn, it simply isn't heavy enough to contain enough propellant to take it as far as a newer AMRAAM. The early varaint, sure. But considering the generation of its inception, that is a little like comparing an Archer to a Sparrow.
Most sources claim a 50km range, but it can be inferred that the range given is an A-pole figure: so the performance is unlikely to increase at higher altitudes. The ACIG article also suggests, as do analysts on DID, that the figure is likely an exaggeration: its performance head-on is closer to 30km, and about 1/3 on a tail chase. That's not too much more impressive than most modern WVRAAMs.
The long range BVR missiles were added later only with the lastest Aim 120D, Russian counterparts and now METEOR. Even Astra is reported with a current range between 40 and 50Km only, while the goal is 80Km or more in later stages. So Derby is indeed a BVR missile, but since the Israelis didn't developed further upgrades of it, it remaind with the initial range specs.
Technically, anything with a range over 10km is BVR.
But the point is, this missile is more of a bridge between the short-range Pythons and the longer range AMRAAMS. Even with the LCA, Derby missiles will be superseded by the Astra, or possibly the T-50 variant of the RVV-AE. Or, depending on the IAF's feelings about it and the radar used, even the Meteor.
Don't get me wrong: I'm not questioning the validity of the Derby as a missile. What I am saying is that it isn't actually the BVR the maker is trying to portray it as.
There are news now from Israel, that they want to develop a new BVR missile, based on the Stunner missile and with 2 x different seekers at the same missile, not to mention way more range.
Yes, I saw that: they've taken the MICA/R-27 concept even further. Twin seekers in one, that's going to be hard to shake off when its on your tail. But, with Raytheon's involvement... I doubt India will be able to purchase it for use on our aircraft.
http://i1173.photobucket.com/albums/r598/DrSomnath999/RAFAELDERBY.jpg
http://www.vayuaerospace.in/images1/M-MRCA-The_contending_missiles.pdf
Already been addressed in my previous statements.