In the Unwrap editor, the Select menu has a tool for this. http://help.autodesk.com/view/3DSMAX/2017/ENU/?guid=GUID-2AEF6A44-859D-434E-8E08-00D2A480A0CD
Looking at the example you provided and as you are in max 2017 - just click with shift held down at the start edge and drag to the end edge, man :smile:
update: i created a spec map and threw the turret into UDK...let me know how it looks now.. http://farm5.static.flickr.com/4037/4266296869_8b1c20c5d9_b.jpg
Hi, I'm a 3D generalist in Taiwan. Familiar with modeling, texturing, look dev, lighting and muscle simulation. Here's my reel from 2015 to 2017. https://vimeo.com/238800997
Haven't found a thread for this. Hopefully some folks might find this useful: https://magazine.artstation.com/2017/08/naughty-dog-uncharted-4-lost-legacy-art-blast