I am going to my first build and I have some questions about the lower parts.

I know there is are vast choices when it comes to triggers, but triggers aside.. do the parts really matter?

The lower i am building is a Dark Storm fixed mag unit, so there will be no magazine release

But for the safety selector, take down pins, trigger assembly pins, and bolt catch... are there really differences between the manufactures and would they have an impact on the guns performance?

I am looking to put together a quality and somewhat accurate build using an Aero Upper and bold, with a Faxon Barrel and free float hand guard.. so i would like to have decent lower parts if they would make a difference.

After you build a few you will know the answer.

Quality parts kits are similar when building, a substandard part kit is a PITA.

Enhanced Takedown pins are nice. How about a B.A.D Safety.

I'm not really sure that it matters very much if you get a kit that has inspec pieces.

I've used PSA, Anderson that I got on sale.  I have some LMT/BCM and a Larue also.  Can't tell much difference usually.

Triggers I always replace with a MBT, very hard to beat at today's prices.

Yes it matters. However, that doesn't mean good functional mil-spec Unites States made parts can't be had for a budget price.

A cheap one will usually get the job done, and may require some fitting but the installer (so it’s a great place to start building, you learn how to fix small stuff, and learn what you don’t like).

I’ve noticed on the cheaper ones that usually the takedown pins don’t fit as well and the safety selector is clunky as hell.

I’ve seen several cheap MIM kits start rusting after a short time in the safe in a humid environment as well.

Are PSA parts kit (like the ones you get with build kits) of good quality?

Looking at a couple of build kits for some strip lowers I have.  Would be getting ones with the EPT triggers.

Honestly there's two tiers.  Cheap MIM crap that isn't very well made, and reasonable quality without paying an arm and a leg.  Aero Precision and DPMS are my two go-to versions, the DPMS is usually able to be had for about 20-25 at Brownells without FCG or pistol grip, and the corresponding Aero is $25.55 at armorally at the moment.

Yes, never had an issue w/PSA LPKs

JP is quality and sells a kit without fcg that is priced nice. I wouldn't order something cheap when you can have quality for not much more.

You can find Colt kits without fcg for $50 and I have had really good luck with Sionics and SOLGW kits without trigger as well. They are around $35-40

I have seen too many broken bolt catches, out of spec parts that don't fit to take a risk on crap brands

Rule of thumb: If a manufacturer makes good guns, then so goes their parts kits. There might be exceptions but quality usually follows the name and the price.
But in the same breath, I have not had any issues with Anderson or even AR Stoner LPK's. I'm sure there is some junk out there, but I have not found it.

Two things I did not do from the start, but regret not doing now:
1) Keep a detailed inventory list of the exact parts you use in each of your builds especially if you have a bad memory such as myself.
Then if you experience a failure down the road, it is easy know what to avoid next time.

2) Try to keep your birds flocked together. I've been screwing around with AR's for a few years now and a lot of my parts are all mixed up. A few of my LPK's got broke up- some parts went to builds, others substituted for upgraded parts, and some went to my spare parts containers. I attempted to clean up my mess tonight and I was able to 'make' 3 complete LPK's and 1 w/o a FCG just from cleaning out my build area/parts storage! They are Heinz 57 kits now but they'll do the job for future builds.....

I got two ar-stoner parts kits. Of the two, neither worked. The first one was machined so far out of spec the trigger wouldn't reset, was missing a take down pin spring, and the safety selector wouldn't turn without an ungodly amount of force. I dropped an old safety selector from another rifle in and it would rotate with no issues.

The second kit was even worse. It was for an ar-10 even though it was packaged in the ar-15 bag. Again, the trigger from it was machined so far out of spec it wouldn't reset, plus the take down pins we're useless since the sizes are different between the ar-10 and ar-15. I finally just ordered some CMMG parts kits and used those. As for the ar-stoner kits, I grabbed the parts that were actually usable, tossed those in a box, and tossed the rest of the garbage in the garbage where it belonged.

I'm glad you've had better luck with them, but they are certainly hit or miss.

I bought a couple no trigger group kits. MIM city. Mag catch, mag button, bolt catch, and selector appear MIM. I guess they would function but not something I would buy if I had known. The mag catch is non standard and has flats down two sides with no threading on the flat sides.

There are a lot of cheap crappy import MIM parts kits out there.  For most people it wouldn't matter, I don't use them though.

School me on this- Do the highest quality or true 'mil-spec' LPK's not have any MIM or investment cast parts?

Even in some of the better kits I've used (Rock River and BCM to name a couple) some of the parts-especially the selector, bolt catch, trigger, and hammer appear to have a 'cast' or 'molded' look to them. I used a Seekins bolt catch in a build once- it definitely looked like it had been machined from barstock.

Just a side note:

I live about 10 minutes from LW Schneider. (if you are not familiar with them- they are a huge volume manufacturer of firearm parts) On their old website they stated that their minimum order was 5000 parts! Their 'capabilities' page is just a small snapshot of the amount and variety of parts they manufacture. Schools you on how many parts ARE NOT made in house by firearm manufacturers.

L.W. Schneider

Pretty cool intro video on their home page. Gives a sneak peak at upper receivers, bolts, lowers, and a few other AR parts during manufacturing.
I've never been in there- I heard they don't give tours

I'm also about 10 minutes from MMC Armory

I need to get a tour of that place for sure......

I do not know what exactly cheap refers to. But I do have a home built AR I put together about 5 years ago, Cannot remember which one. But I believe it has a CMMG kit, but could have been DPMS. It has never been a safe queen. I do not know if 4000 or so rounds is alot. But it has atleast that on it, and never one problem.

We are building a A2 with my Son right now. AR lower is Aero so I assume the parts kit is too. I do not expect to see any problems there either. These are shooters, we are not likely going to battle with them any time soon. Especially the kid,LOL

If something works at a good price. No problem for me. Low price does not always equate to junk, but yes, occasionally it does.

I've been using Damage Industries parts kits with good results.  They produce parts for other companies.

I've had issues with PSA lpk.  The take down pins on 2 different kits.   They send you what you need if you have an issue.

For my lower builds I generally assemble my own kits of known quality. They aren’t the cheapest option, but I know they’re safe, reliable and top shelf quality.

Pistol grip: Whatever your preference, the default for me is the rubberized Magpul MOE grip.
Pistol grip Screw: V7 Weapon Systems titanium grip screw
Receiver Extension: V7 Weapon Systems 2055 lithium aluminum receiver extension. The lightest, toughest extension you can get. The extension offers a significant number of stock positions over the typical extension. If using a stock that doesn’t require a carbine receiver extension, plan accordingly.
Receiver plate: V7 Weapon Systems aluminum receiver plate.
Buffer: JP Enterprises Gen 2 Silent Buffer with extra spring pack.
Buffer Retainer: V7 Weapon Systems titanium retainer, comes with the spring. I install these even with the JP silent buffer since I don’t like the buffer just falling out.
Trigger Pack: Geissele all the things, whatever flavor desired.
Trigger pins: Use the Geissele or if you’re chasing lightweight, throw in a set of V7 Weapon Systems titanium pins spec’ed for the Geissele trigger.
Bolt Release: V7 Weapon Systems S7 steel bolt release with spring, plunger and pin. Or the Battle Arms Development billet bolt release. Both are nice and will beat any MIM parts any day of the week. This is particularly important in pistol caliber builds.
Takedown pins: Battle Arms Development enhanced pins. Titanium if you’re chasing lightweight. These will come with the detents and springs.
Magazine release button: V7 Weapon Systems makes a nice button. This should come with the spring.
Magazine release catch: Norgon Ambidextrous releases are the best out there if applicable to your lower.
Selector: Battle Arms Development CASS Short Throw selector. Long/Short thin levers. This will come with a quality selector spring and detent. Depending on your lower, you may have to file down the lawyer pin on the selector core to get it to fit in to your receiver. The CASS is a better design if the ASS.
Trigger guard: If applicable to your lower, I’m partial to the Magpul enhanced trigger guards pattern.

I read another posters recommendation for the Strike Industries Enhanced LPK and then looked at what you get. It does seem like a solid deal, especially if you are doing the kit less the trigger, I just wish I could find it for about $30-35

I started building AR's with CMMG parts kit, I tried a PSA one time.  Parts were rough machining and not smooth.  I returned buying all CMMG gun builders set.  High quality parts.  You can catch on sale for $30.00 shipped.  I bought about a dozen then.  I never use mil-spec triggers or grips.  Good shooting