If you are looking for arrow shafts, look up your local archery club, go to one of thier 3d shoots, you will find lots of shafts there. Cheap...
I cut two channels in the barrel channel, one on each side of the front sling swivel running back to the recoil lug, then I fit my arrow shafts and glue them in with archery glue for carbon arrows and let it cure. I then mix up a batch of fiberglass resin and fill up the barrel channel to cover the remaining crossmembers in the stock, but I still leave quite a bit of clearance for the barrel.