Can someone please explain what a "Nowlin Ramp" is? I'm seeing a lot of guns for sale with them at AR15.com, and I've never heard of them.
It's really a Wilson/Nowlin ramped barrel. It's mainly for aluminum framed guns. Certain kinds of hollow point ammunition and magazine followers will dig pits and grooves into an aluminum frame's feed ramp. This is a stop gap fix at best. Ramped barrels started out as a fix for old GI issue steel framed guns that had been buggered by an incompetent gunsmith or guns that had been badly damaged during firing. Now, some idiots are marketing them as an "improvement" for steel framed guns.