Did yours come with an inspection booklet with the "certificate of accuracy" ? If the factory shot five shots that weren't half bad, maybe it is something about the ammo. You'd figure they'd catch one that was acting like a complete sewer pipe.
A guy with a drill has probably heard of a center punch. And the other parts aren't hard to find. The point is that if the ATF doesn't like a feature, it's not the sort of thing you want to argue with them about. Unless you're filthy rich, of course. Those attorney fees will add up quick.
Looks for all the world like a drill guide - make a full auto just by drilling a hole right here -->. No wonder they're excited. It's their job to get excited about that sort of thing.
There's a US-made handguard for the HK MP5 that is almost a bolt-on. Just needs minor fitting and hardware. It's about $50 shipped. It won't get you any rail space, though.