Colonel Whelen asserted the very small remaining portion of the .30-06's 17° 30′ angled shoulder was likely to cause potentially dangerous headspace difficulties. The headspace issue has been widely discussed. Frankford Arsenal machine shop foreman James Howe necked down cylindrical brass available in the arsenal manufacturing process to form cartridges with a -inch-diameter ( mm) shoulder to fit the chamber of his rifles. Experimenters had less success forming cartridges by enlarging the necks of .30-06 cartridges with -inch-diameter ( mm) (or smaller) shoulders, but could form brass from .35 Whelen cases.