The detent ball seating into the backside of the actual aperture is an inherent PITA with any true patterned Hadley eye cup.
A.) If properly maintained (e.g. lubricated) it attracts every dog hair and cottonwood fluff in creation,...run dry the BP gasses make short work out of the detent ball spring, and the disc winds up seized or free wheeling.
B.) The largest size one can incorporate into a Hadley is limited by the size of that detent ball,....and typically pretty damn SMALL. That can be a hateful situation in poor light, and stalking targets on a shadowy berm.
One solution is for the builder to put in a series of offset detents, in other words out at a larger radius. Certainly do-able with a good rotary table on one's mill, and a little patience.
I can tell you one thing, the Merit system requires lubrication as well, when used in a BPCR application.
GTC
