Robinson Arms is a good choice
It will be general use. Training and for what we all hope never happens. In my area I anticipate typical urban distances of 40 to 100 yards, possibly out to 300. I already have a 10.5" 5.56, and a 11.5" 300 black, suppressed. I don't prefer the shorter barrels. They are handy, but try shooting one in a enclosed area. I don't want to be deaf and blind in a gunfight. Not to mention the significant loss in volocity. I would prefer to buy a proven factory model over building.What is the purpose of said rifle? Home defense? Urban patrol? Shooting 600 yards across a field?
I’m not a Knights fanboy. Nothing against them, just overpriced, IMO. Scar? No way. That thing needs too many upgrades for a rifle that should cost half as much.
Me, for HD or neighborhood patrol, I’d build an SBR, with a 11.5” barrel in 5.56 or a 10.5” .300BO if you want to go that route. Put a lightweight barrel on it, sling, flashlight and a prism optic. It would have to have a nice, crisp 3-3.5lb trigger and a thin handguard. Call it good and shoot it. Add a suppressor if you really want it.