Yup, that's why I like alpha mike foxtrot even though serial is probably a better choice. You can count on one shotting most things even if you graze.Plus it's pretty entertaining when your top sniper gets a 'graze' for 13 or 14 damage that outright kills the intended target anyway. Perks of using high-caliber weaponry, I guess?
Yeah the method I found is tedious, but it's fundamentally reliable (suppression + cover = you have very low chance to get hit, and you use grazing fire and just volume of fire to hit them in their cover), in fact I'm already exhausted of it and another supply raid came in one week after the first so it's omg again? And this is the second month T_T
I think there's a point at which you don't need to farm supply raids anymore, and that has to do with enemy composition and your economy, but that comes much later in the game. I can't really imagine this working out too well when codexes show up, or even just a bunch of yellow alert longbows would be annoying AF.