Also what are your times, temps, developer and technique on your HP5? Personally I'm loving it at 800 for about 15min with Rodinal 1-50 but its certainly not grainless. For less grain I use Tmax 100/400 or Acros.
Also getting some nice look at 320 in HC-110:
Devil's Tower Tele-Rolleiflex IlfordHP5+ HC-110dilH by rich8155 (Richard Sintchak), on Flickr