I really think they could have easily upgraded the FNC with a few engineering changes reducing the unit costs and making a superior product with a few modern manufacturing techniques. Like change how mounting the barrel and head spacing along with the gas block. They were never thinking about replacing barrels, timing, head spacing and gas block installation. They figured once the rifle was built, you probably wouldn’t have to ever do it. And because of that, most bolts will not headspace between other rifles. You have to mount and headspace the barrel first, then drill a gas hole, then install gas/sight block. I think that was probably the biggest downside to the FNC, where as you can relatively easily change out an AR15 complete barrel/sight/gas block assembly, drop in a bolt carrier and headspace is usually good to go. I always wondered why they left the magazine release button unprotected from accidentally hitting it. The AR platform added the raised area “fence” many years ago.