I want to upgrade my AR to better suit an appleseed. I plan on using the A2 sights/carry handle but I need to find a free float tube to attach the sling to. Do they make National Match handguards in carbine length?
Can't say that I've ever seen one in carbine length. Of course, you can always just run any free-float rail system to accomplish the same.
Though I will say this. If you're looking to have an appleseed-ish AR, I would strongly suggest finding a way into a 20"er.
I'm sure 210+ has been achieved with carbine length irons by a few people, but the geometric advantage of a longer sight radius is invaluable.
Edit: If you go the rail mount, you can always just run one of these (https://danieldefense.com/mounts/sling/rail-mount-qd-swivel-attachment-point.html). I do.