The heart of the A-510 bore target is the removable adapter, the A-510A, B or C. The bore adapters are customized for each barrel diameter, but can handle +/- .040" of diameter variance. The patented target and adapter are specially designed to find the center of the bore, without any moving parts, to a tolerance of .0005" (with care, tolerances of .0002" can be achieved).

The target is designed so that the PSD is centered axially between the 4 feet of the adapter, 2 of which are offset axially from the other 2. This, in effect, puts the PSD on the pivot point of the adapter and allows the angle of incidence to the laser beam to vary by up to 45º. The A-510 takes advantage of this property by making the adapter slightly larger than the bore. To insert the target into the barrel, a spring-loaded pole is attached to the target and the target cord is pulled. This tips the target forward, allowing it to easily slide into the bore. When the cord is released, the target and adapter "jam" into the bore, finding the center automatically. The weight of the pole keeps the target centered in the bore.