I have just gotten a .17 cal. single shot from New England Firearms it is the Sportster model .17 Mach 2. I am getting split casings about every 5 shots. I have marked the casings with a permanent marker on the top. When I eject them the splits are on the bottom of the cartridge starting from the top of the bottle neck on some and on others it splits on the shoulder and some split all the way down to the rim. The primers are not buldged either. I have tested both Hornandy and CCI and gotten the same results about every 5 shots. If anyone could give me some info on this that would be great.
Since the heads aren’t puffed up like the gun has headspace it is that the chamber is oversized. It splits on the bottom because the extractor is pushing the case up to the top of the chamber and when it expands under pressure it is always down.
