There are a couple of sleazy ways to beat it:
1) Build a crap ton of 1 msp missiles that are nothing but a cheap reduced power engine and a dinky bit of fuel, that you can therefore fire at a waypoint from a billion km away. Fire those in the general direction of the enemy and they will often fire 3 AMMs for about 1 BP each at missiles that cost you .05 BP to build
2) Find out their exact AMM range. Dance on the edge of it, go in, draw their fire, run away, missiles explode in space, repeat until enemy is out of missiles. It can be expensive in scouts to determine their exact range, but once you have it, all you need is to have some units that are small and distinctly faster than the enemy fleet.
3) If you don't know the EXACT range, dance on the edge of their range with heavily shielded warships, take some hits on the shields while running away. In either case, you want a really overpowered res 1 sensor to give you time to react and to help you calculate their exact range.