PEW Science has published a new sound-signature test of the Otter Creek Labs Infinity 556K on a 10.3-inch MK18 firing Federal XM193 ammunition. The July 29 test examines how the suppressor behaves with its solid, partially vented, and fully vented end caps.

The Infinity 556K earned an overall PEW Science Suppression Rating of 36.4 with the solid cap, 38.0 with the partially vented cap, and 33.8 with the fully vented cap. In this particular host-and-ammunition combination, the partially vented configuration produced the highest overall rating of the three. The included partially vented cap therefore was not simply a midpoint between the sealed and most-open configurations.

That result matters because the Infinity 556K is designed around interchangeable end caps that change system behavior. Otter Creek Labs describes the suppressor as a 5.5-inch, .243-caliber model for 5.56mm and 6mm cartridges, with a 1.375-24 HUB-compatible rear interface. PEW Science tested the unit with a Rearden Atlas mount and single-port brake; the suppressor measured 6.125 inches and 18.9 ounces in that tested configuration.

The numbers should be read within the limits of the test. PEW Science's Suppression Rating is its own comparative metric rather than a simple peak-decibel figure, and the organization advises readers to examine both muzzle and shooter-ear results. The findings apply to the tested MK18, ammunition, mounting setup, and end caps; they do not establish identical performance on every rifle. GunsNation has not independently tested the Infinity 556K.