To the OP:
I own a SCAR 16S and SCAR 17S...
Lets see, it uses a short stroke piston. Not much different than my Ruger SR 556 Piston but thats where the similarities end.
The SCAR 16S does not have a transfer rod as found in many AR15 type gas piston guns, the piston on a SCAR impinges directly on the Bolt Carrier Group. A 'regular' gas piston AR15 works by gas piston pushing on the transfer rod and then rod impinges on the bolt carrier group.
The SCAR's barrel can be swapped out by the owner at home using a torque wrench, stock is fully adjustable. Length of pull, cheekrest height, and folds. The gun can be fired while the stock is folded. You can switch the charging handle side with partial field strip of the firearm. The firearm can be field strip for cleaning with no tools after pushing out one pin. Its modular in design
Here's a video to show how easy the SCAR breaks down.
I'll check out this thread every now and then if you have more questions.
My opinion: great gun! Lightweight, light felt recoil and accurate!