All I know for sure is Roundup you buy today is not the roundup from yesteryear! Anybody got a better choice for total kill dont want anything there type results. Think gravel in pistol range. I have sprayed with round up and it just don’t phase it.
My neighbor with 40 acres qualifies and goes to the county extension office (AG) and buys the commercial stuff. I in turn get what I need from him.
He gets commercial roundup, a brush killer and a weed control that won't kill the grass. Works well doesn't take much mix with water.
Check your local office.