I’m collecting parts for an AR build. Only have the receiver currently. Which parts are the most critical, that I’d want to spend a little more for quality parts? Im thinking barrel, BCG, trigger. Any opinions are welcomed.

I would add adjustable gas block to your list, and pistol grip if you have a preferred grip angle.

Wilson Combat barrel and a good trigger will affect accuracy most. A quality free float tube is also a necessity.

Barrel for sure. There are a lot of good barrel makers for ARs but I don’t think there is any better barrel for the price than the ones made by ARP for $200.

What do you want the AR to do? Shoot small groups? Hit man size targets at 100yds? CQB/home defense?

Good question, and I don’t have an answer since it just seems to be a beginning hobby right now. I was thinking of a shorter than 16” barrel and a suppressor. After doing some research on the ATF pistol requirements, it may end up as SBR. Which I’m thinking is not so much for small groups, but home defense.

I’m currently on the same quest. I’ve been looking for a quality lower.

I picked a PSA lower, $75 after tax and freight, not including the transfer fee. Not top of the line, but it’s my first build. I hear Aero is pretty good. And has some sort of set screw to take out slop between the upper and lower, if I read the info correctly.

If you’re going for a pistol or sbr then I’d probably buy a complete upper from a reputable mfg that way you’re not wasting time and $ troubleshooting any issues. I wouldnt worry about high quality barrel if you’re not shooting for accuracy. PSA has tons of uppers to choose from that will keep your upper and lower matching and will be plenty accurate and reliable. I used to piece together ARs when I first started because it was fun but quickly realized that they didnt hold resale value like a complete gun all from same mfg. Once I figured out what I “needed” (wanted) I sold off my franken ARs and just bought full guns from the best mfgs in the game.

Just my opinion, but I prefer to get as much as possible from one company. They usually go together with less hassle. How many times have we seen someone asking for help on the forum because they have a problem with their rifle? AND then they list off 10 manufacturers when you ask them to describe their rifle.

I still keep my eye out for savings, but I hate having a new rifle with problems. The worst thing is sitting at the range thinking, "I could have done better!"
I stick with Wilson Combat, but there are times when I wait for them to have a good sale going.

Thoughts on Aero uppers and lowers?

They are good to go. Not top of the line but they make great, quality stuff. I wouldnt have any 2nd thoughts about Aero

I’m going to SBR this lower, so I want to buy quality.

The barrel is the most important part. Mil-Spec will work for all the rest as long as you understand how it works.

If you are going to make the investment ($200 stamp tax) z as me 6-12 month waiting period then don’t go cheap with a run of the mill stripped forged lower. Buy a billet lower ($250) because you are stuck with this lower forever. Just off the cuff Seekins makes a nice billet lower.

My first SBR was on a Spikes Tactical $100 stripped lower. Looking back (+10 years), the amount of time and money on parts building out the gun makes me wish I had spent the money to upgrade the lower to a nice billet lower with a flared magwell, integrated trigger guard, and maybe even with ambidextrous bolt catch/release buttons.

Even better is a matched bullet receiver set. Next best investment is barrel, trigger, and adjustable gas block.

This is sound advice. If you’re gonna drop $200 to the ATF and $50-$100 to have engraved, get a nice lower. Waiting period has been more like 6-12 days lately so nothing to worry about there right now, could change quickly if pistols become NFA items here soon. Personally, I like SLR matched receivers these days.

Just my two cents worth, but having built over 20 AR's in both large and small frame receivers in a multitude of cartridges these are the parts I feel matter: Barrel, Bolt, Trigger, and a Handguard that is free floating (in that order). If you are going to do anything other than 5.56 then I would make sure the bolt and barrel come from the same manufacturer. I have built a bunch of AR's on Aero receivers and have never had a problem with them (both new and blems). I have also had very good luck with Ballistic Advantage Barrels (Aero own's them) and Fail Zero bolts. Triggers are personal preference but I have used Geissele and TriggerTech triggers. Depends on the use of the firearms as to whether I use a single stage or a double stage trigger. I would recommend building on a forged receiver instead of a milled billet. Billet receivers are typically not as strong as a forged receiver which is why most are machined differently. They add material where needed to overcome these weaknesses. If you are going to spend the money on a tax stamp (to SBR it) then I would recommend a forged receiver and either a Noveske, Lewis Machine & Tool, Bravo Company Manufacturing, or Aero Precision. I'm not saying there aren't other quality receivers out there, I'm just stating what I would use if I was going to spend the money on a tax stamp. I would want the firearm to be quality and of some value for which any of these receivers would fit that bill.

Thanks for the info y’all!