This isn't quite 100% true. While rapid-fire weapons will generally gain adaptation counters more quickly, there is an internal limiter that prevents you from gaining any adaptation counters for a single energy type for 0.4sec after receiving one.
So, for the Autocarbine's primary fire (e.g.) you should only ever receive a maximum of 2 adaptation counters, which would only happen if you hit the refresh cycles exactly perfect. It's statistically less-than-likely, but not out of the question. Since you only have to remodulate after receiving 4 adaptation counters for a particular energy type, you should always be able to get 2 full primary fires with the Autocarbine before being adapted. Sometimes up to 3 full bursts (12 shots) if you get lucky.
yah the numbers there might need some further tweaking, it still feels too fast, in particular the secondary fire is a sure instant-adaption trigger.
also please take a look at the weapon model (/forward to the artist who made it), the textures on top of the gun are... *wobbeling* a pixel left and right all the time.
One thing I don't get is why they have shields AND the adapt shields when the adapted shield WAS their shield. either remove their shields are make it not adapt once their shields are gone. it kinda stupid for them to get dual shields.