Instructions
Download "The Passing" for "Left 4 Dead 2." The content is available on Xbox Live for 560 Microsoft Points and free for PC and Mac players. Install the extra content to begin the campaign.
Play through the campaign missions of "The Passing." Although rare, M60 weapon upgrades can be found throughout the campaign levels at different places as determined by AI Director (the game's system of artificial intelligence). As with the chainsaw and the grenade launcher, the M60 comes with a set amount of power (150 bullets) that can't be raised at all. Once the gun is dry it is discarded and can only be regained by finding another M60 upgrade.
Take part in the weekly "Mutations" included with "The Passing" add-on. The specific game modes are changed every week and played outside of the regular campaign. One game in particular, Gib Fest, allows players to only use M60s and Magnum pistols.
Download later content patches, "The Sacrifice" and "No Mercy." These two patches further add to the "Left 4 Dead" and "Left 4 Dead 2" stories. The M60, having been introduced in the earlier content, is again made available for these new levels. While the content is available for both the original "Left 4 Dead" and its sequel, the M60 can only be used in the "Left 4 Dead 2" version of the add-on.