What are you talking about? The Locust's margin of error is a whopping six hexes at the minimum, and 18 hexes if you're using the LRM.
I think you're misunderstanding. I mean that you can't let the Charger get within firing range once. If you were using a Wolfhound, it could take some punishment, but iirc this is the most frail (non-industrialmech) mech ever created. This means that the Charger will have control of this fight, despite its lower speed, because the Locust is going to be desperately scrambling to avoid that Charger the whole time.
A single ton of LRM-5 ammo MIGHT be able to kill a Charger, but with no ammo, and the expendable nature of its side torsos and arms, it's not likely to kill the Charger outright. Then begins a long, tedious game of cat-and-mouse, where if the Charger gets in a single shot, it's pretty much over. And with only two mapsheets, trying to flank the Charger requires VERY precise movement. If you think about it, the Charger doesn't have a 3-hex range, it has an 3-11 variable range, based on terrain and turning.
In short, the Locust theoretically can win this fight,
if the Charger never closes even once, and
if the Locust never falls down for some reason. With the small maps given, that's some slim odds, right there.