High accuracy at 260ft can be achieved with a 5" barrel.
This is why the whole dmr thing is a laughable idea in airsoft.
Anway, theres always talk of running an inner in a suppressor, but the smarter thing to do is to run a shorter barrel in your outer barrel.
20" outer barrel dmr with a 12-14" inner barrel.
The shorter barrel will offer just as much accuracy and be less susceptible to fouling.