Finally got a few minutes and did a quick round of testing direct fire LRMs vs AMS. Oddly, it seems the AMS shoots down missiles faster at close range (time 2:40 - 190 meters) vs. long range (time 0:25 - 800 meters). Explosions right at the mech launching them instead of near the cockpick of the targeted mech. I will see if I can do some IS LRM 20 testing tonight and see if any missiles get through. I think we can very, very safely say, don't use single launchers or chain-fired LRMs. So if this is the buffed speed, spread and angle of attack, indirect fire would be quite a bit worse.
When the launcher is inside the range of the AMS, I wouldn't be surprised if it's getting the missiles before they even get to maximum speed. Or even inside the launcher.
