The US Military has and probably will again in the future sell upper receiver assemblies because they are not the items needed to create a fully automatic rifle.
I missed out on the sale of M16-A1 parts kits a few years ago due to broke-itis. It had ever part except for the lower receiver and trigger group. I really wanted one since that was the weapon I carried my entire active duty time and I qualified expert in basic training with one. Great super light little rifle.
Okay for all the Garand, M14, and BAR fans out there I’m going to bring you painfully into the 21st Century.
Before I go on I want to let you know that I have a CMP Danish VAR barreled Garand that I cherish and love to pull out of the safe to just lust over how sexy she is. I take her out and shoot around 40 rounds a year before I lovingly clean and re-grease her before putting her back to bed in the humidity controlled safe.
The Garand and M14 are incredibly reliable, durable, and idiot proof. That being said.... they have a couple flaws in their design. They have (very expensive) receivers that are complicated, expensive, time consuming to machine, and quite frankly outdated to produce.
The gas system with the intricate op-rod and integrated long stroke piston inherently becomes more inaccurate with every single shot. It takes an artist with years of experience to put a new piston tip on, bore out install and/or lap a gas tube, or hand fit a stock so it’s tight enough to be accurate.
Meanwhile, my .308 SCAR-17 is just ridiculously accurate with only a 16 inch barrel. Need a new barrel? Undo a few hex head screws and pull the old barrel off. Install the new one with a new bolt and you’re good to go. The gas system is a fully chromed short stroke piston design. It doesn’t shit where it eats and piston or gas tube wear doesn’t affect accuracy. Oh, and it weighs about 8 lbs loaded.
Make a SCAR for the .264 USA cartridge and with an optic you can now easily engage out to 1000 yards.