Having tried a few backing lines for shooting heads if i read you post correctly, its the actual line behind the head you wanted to know about?
Anyway 20lb amensia in yellow works best for me (colour yellow tangles less apparently according to my locals). For pure distance you cannt beat it.
For general nice fish ability and slight more expensive is braided nylon backing ie tube shaped. Mullakeys here is the best as its springy and not limp. (Forget the limp stuff for distance work as it locks solid.) This has to my personal fav as it doesnt tangle half as much as amenisa and fig8ing is great. Also untangling factor this stuff scores highly and if u playing with shooting heads you will get them
Airflo polly shoot. Does what it says on the tin. Not sure if they make it anymore. Works well but the most expensive option is the negative also to nail knot it using the core to the head is a tricky job, to get a seemless link. Lost a few heads with this stuff too due to snapping. (you cannt knote it using the full coating and nylon core). Overall works fine.
There are couple others i have tried ie flate mono etc but the top 3 above is kinda what i always ended up buying again.