Originally Posted by
303Guy
OS, that is looking very good. I would have thought .34/.35 was the node. Or another node anyway.
On velocity not being what is claimed it should be, I have two rifles - 303 Brits. Same load in each rifle and one produces considerably higher pressure. The difference is in the throat, bore and chamber. I don't think it's so much a larger bore taking more energy to expand the case but rather, the larger chamber lowers the pressure by giving more volume. Then there is free bore/large throat volume with less initial resistance plus a larger bore. With a 22, I would think it's simply the larger chamber volume. Remember too that a larger chamber gives more room for the crimp to expand into so maybe there is just more crimp grip in a tight chamber?
I do know that my 512 produces the claimed velocity of CCI sub-sonics, that being 1050 fps. Although, that cool evening I was getting quite a varied sonic crack so velocity must have been varying. I would have thought Eley would be measuring their target ammo in a target barrel but I suppose those can vary too. OS, how tight is your rifle's bore? I have two rifle barrels that are tight enough for a 22 air rifle pellet. That's to say, the head rides the lands. I wonder whether that would raise pressure and velocity?