i have read an artical on "brush busters" they put up a target and shot through some twings and such and they used calibers ranging from 22-250-510 nitro. and this was there results
top 5 "brush busters"
1.22-250
2.243
3.270
4.510 nitro
5.7mm mag


if i were in your shoes i would look at something in the 7mm range. weather it be a 7mm,7mm mag or 280 they will all do what you are looking for.