Looking at BC's in that pellet range I would use 0.035 and you won't be far off. There are programs around if you have a crony that will give and answer.
The Predator GTO (alloy) in .22 has a BC of 0.023 (cf. BC data base of HardAir Magazine).
The GTO is somewhat comparable with the lightest domed lead JSB (RS) which weighs 13.43gr, with a BC from 0.023 to. 0.026 (depending on who measured, and how). For comparision, the Predator alloy pellet weighs 11.75gr. Because of the alloy the pellet is much lighter, which lowers the BC because the sectional density is lower. I would guesstimate at least 0.020, and potentially higher.
HAM measured the lightest .177 domed lead JSB (RS) with 0.023 (some others up to 0.026). It weighs 7.33gr, quite close to the GTO (alloy) at 6.78gr. So, I would assume 0.023 as base line, and potentially higer.
I started a thread on this topic. No reason a starting point couldn't be printed. (Bc .032 @ 800 fps). We can figure out the rest. One should not have to hunt for this info..