I've been using plastic bags inside burlap bags for years. We get animal feed and bird seed in 100 pound feed bags that are made of a "plastic burlap." I stuff these with plastic grocery bags, Wal-mart bags, and plastic drop cloths. Stops my carbon arrows fine.

One thig I did find out, don't stuff them with those blue plastic tarps. It stops them great, but wicked hard to pull out.

After the bag itself is getting worn out, I just slip a new burlap sack over the whole thing. Just like new.