I've been wanting a 14.5" ar for sometime so I decided to build one. I started with a DD upper I already had from a complete rifle. I wanted the whole upper to be DD but they don't offer a gasblock that isn't clamp on (you can't buy barrels from them so getting on with a pinned gasblock isn't an option). So I decided to go with a bcm set screw. Found a 14.5" lw barrel on clearance at midway and got a DD slim12.0 handguard. Went with a bcm a2x flash hider since it came predrilled with a pin for permanently attaching. So I get it all together, muzzle device pinned and welded and go to the range. It's nice and light and runs perfectly. At this point I'm very happy with it. Get home and start cleaning and looking it over and I noticed the gas block has a mark length wise on both sides. The handguard is so slim in the middle that the gasblock is making contact when the barrel whips. I can take my hand and apply light pressure on the end of the barrel and make them contact. I ended up pulling the handguard off and contouring the bottom of the gas block to the shape of a DD gas block. It no longer touches, but what a pain. I thought it would be helpful to post this as so many people are buliding ar's and superslim lightweight parts are the new thing. (This is not my first build nor my first time using the DD slim handguard. Last time I had a barrel straight from DD and I had them include a lo pro gas block and drill and pin it for me. Obviously their gasblock is small enough to have proper clearance.)