 Reloadable cartridge cases are produced by reforming .30-06 brass, or fire forming 8x57mm IS cases.Case heads derived from the .30-06 are slightly undersized and bulge slightly just ahead of the web on firing, while the 8×57mm IS derived cases are slightly short.Normal cases of the correct dimensions also bulge slightly, however, as most Japanese rifles of this era had slightly oversized chambers, intended to allow the bolt to be closed on a round even in a very dirty chamber.