21st Century - Case Holder With Driver Size:408 This points to you having

This points to you having a very tight chambered gun and would assume either an improperly cut reamer or a chamber that was cut below Min Chamber Dimension headspace

The High Master Lens System has 2 Super ED lens elements within its lens system

Easy-to-use cross bolt connects the two ends of the ring instead of a traditional screw design that tightens directly into the threads of the die

but if there is one of these "New" case holders listed for your cartridge it is a good good idea to have both

Graduations of

21st Century - Case Holder With Driver Size:408 This points to you havingThese case holders and drivers are for the 21st Century Lathe (used on the tail stock) and for hand turning with power driver or drill. To determine proper case holder driver you need for your application please refer to the chart here: