The point is that due to feed jams with the Remote Gun System, the crews have less than full confidence about using the .50 M2, normally a fine, reliable weapon that worked just fine through WWII, Korea, Vietnam, Iraq War I, and any number of lesser conflicts and actions in between. But the flexible mount of the Stryker's RGS has been described as being unable to fire more than 45 rounds before hanging up. Accordingly, it'd be understandable that the crew would be considering the use of an Mk19 as an alternate.