picked this quick 16 for 4.99 at the thrift store..lots of homebrew mod for it to accept a full mag of elites and anti-jam mods.
Here is my no jam mod...2 guide rails along the bolt lug.
Hard to see but there is a special angle plate in the mag well to help keep the darts in better allignment.
Cut out in the feed doors.
It also has a doubled spring for a bit more oomph but unfortunately I have no pics of that one...Hope you guys like them.