This Delrin block diagnoses one of the primary causes of improper feeding in the M1 Garand rifle, a damaged or worn cartridge feeding mechanism. Timing is "off" if the feeding mechanism is not positioning a cartridge in front of the bolt at the correct time, and can be a somewhat common issue as most Garands have seen decades of use. It's a handy tool for use around the shop, and very nice to have available if shopping for a Garand.