Honestly, buy whatever fits your budget and train, train, train. The military uses the lowest bidder and those rifles keep functioning somehow (mine were all FN stamped). You don't need a noveske, seekins, Daniel defense, etc... to get the job done.
The benefit of building both the AR upper and lower is that the builder better understands how the parts relate and function, and how to repair any issues. Cannot beat hands on experience. Beats "reading about it" or watching YouTube videos. Knowledge is power.Building up a lower is simple. There are plenty of youtube videos on how to do it and it doesn't require any really special tools. Castle nut / AR Wrench for the buffer tube, but that's really it. It can be done at your kitchen table. I've literally built mine at the kitchen table or at my desk while on conference calls.
The upper is just slightly more challenging, but still very easy to do. You do need to torque the barrel nut, so you'll need a vise.
My opinion is to build the lower. Get a "cheap" forged lower and standard lower parts kits. Very easy to build.
Then buy a complete upper. I've found that its not really much cheaper to piece one together... and usually more expensive because you end up customizing parts.
The one I built years ago has been a great rifle. Not pretty, but shoots straight. What I started with was a Sarco 'parts kit' from a decommissioned Vietnam era M16A2 rifle. It was my first attempt at building one and I will admit I did have to purchase some extra detentes, but I learned how to get them in with out shooting them across the room. The complete rifle was about $450. I have built more 'impressive' rifles/carbines since. To this day I still shoot that old A2 in my clubs competition, and in a lot of cases beat out high dollar guns. But again maybe I was just lucky and got a good kit from Sarco.Stay away from junk like this. https://www.sarcoinc.com/ar15-m16-parts-kit-flat-top-optics-ready-kit/
You are not a friend telling someone to buy this. You don't even want to go down the junk rabbit hole. They never shoot a good group because everything is cheap junk.
You buy an upper or a barrel with free floating front hand guard. That way the barrel is held on really well to the upper receiver with a big barrel nut. 1:9 twist or possibly 8 twist never 7 twist. most barrel manufactures tell you a barrel weight. The gas block size is an indicator of barrel weight. .750 gas block size is your medium weight. .625 are really light weight. I have 18 and 20 inch barrels in both sizes. I've got away from barrels with threaded ends. It just adds length putting on a flash hider or muzzle brake M-lok hand guards are the some of the best.
I buy forged everything upper and lowers. I've got away from the phoney forward assist type uppers. These are much lighter and trouble free.
AM-15 Anodized Sport Upper Receiver, No Forward Assist or Dust Cover
No Forward Assist or Dust Coverandersonmanufacturing.com
This is a quality piston type rifle 20 inch match SS barrel titanium muzzle brake 9 twist Hogue rubber grips and stock. 3 pound drop in trigger dime sized groups at 200 yards using a lead sled to sight it in.
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The one I built years ago has been a great rifle. Not pretty, but shoots straight. What I started with was a 'parts kit' from a decommissioned Vietnam era M16A2 rifle. It was my first attempt ant building one and I will admit I did have to purchase some extra detentes, but I learned how to get them in with out shooting them across the room. The complete rifle was about $450. I have built more 'impressive' rifles/carbines since, but to this day I still shoot that old A2 in my clubs competition, and in a lot of cases beat out high dollar guns. But again maybe I was just lucky and got a good kit from Sarco.
The first photo cot $450, the second is a F class rifle good for 1000 yards, but I have closer to $4000 in it so I don't think it would classify as 'entry level'
Started with a Sun Devil milled billet upper and lower. Used a Geiselle SSA trigger system. The barrel is a 24" Black Hole bull barrel in .264 LBR-AR (Les refused to pay the copyright fee for the name 6.5 Grendell) with an adjustable gas block. The BCG is from JP Enterprises. The weight was getting up there so I went with a carbon fiber front tube and an Ace skeletonized stock. Tried different scopes, but ended up with a Nighforce atop a 20 MOA base. Because of the weight I named it 'The Pig'. But that little puny round will really surprise youHow about giving us the details on your F-Class rig.