Back to your original question... yes you can change your upper into a dissipator. The dissipator gas block is a normal front sight gas block with the top cut off. All you have to do is cut your sight, remove the handguard retaining plate, get another front sight and full size hand guards. Pin on the front sight in the 20" barrel position with handguard retaining plate. I have one with A3 top and AK brake... best AR I fill I have brough to date.
Full Length Sight Line
No heat build up
Short and handy size
Ugly at first, but its practicality grows on you like a ugly women that cooks good.
If I wanted a 16", it would have to be this rifle.