The flutes on .20 and .17 cal reamers are pretty shallow and don't allow a lot of feed rate, but you need to speed it up to about 90 rpm. This will make for smaller chips that will flow out of the flutes faster.
I use a muzzle flush system to pump cutting oil towards the cutter and I usually run a t 130 rpm. If you have a good reamer, the chips will flow out at such a constant rate that you'll only have to withdraw the reamer a few times to clear it.