Going to get started soon, any lessons learned/pitfalls/super awesome tips?   

Watch a bunch of YouTube videos on the topic and make sure you have a decent set of tools

roll pin starter would help though not necessary.

roll pin starter would help though not necessary.

Yep. The most delicate part install would be the roll pin for the bolt release. Just because it'll Mar scratch ruin your lower if you don't take precaution

Yep. The most delicate part install would be the roll pin for the bolt release. Just because it'll Mar scratch ruin your lower if you don't take precaution

latex?

Watch the part when you are inserting the spring and detents. They make really good and tiny projectiles that are hard to find.

When doing the detents, take a big and transparent plastic tub, turn it on its side and work inside the tub.

Blue painter's tape.  Put some around every area you need to use a tool on.  It'll save the finish from that nasty "slip & scrape".

A bench vise and proper upper & lower blocks to hold the parts while you do the less delicate work, like tightening barrel and castle nuts.  It also acts as another pair of stable hands to make the process easier.

Take your time on the lower parts kit installation.  It's better to get each part right once than to have to take it apart because something is not right.  Identify all the parts that need springs and detents and install those together,  That way, you don't skip the detent and have to take that part off again.

If you are attaching a new barrel, make sure to buy a small packet of AR barrel grease if not included with the barrel or parts kit.  This is essential for the barrel to seal & remain trouble-free.

Buy a spare parts kit with extra springs, detents, and other parts that get lost or worn out.  For such a small price, it can save you a bunch of headaches when a part goes missing or a spring gets destroyed trying to take off the buffer tube to add an ASAP plate.

Know whether the buffer tube you get is MILSPEC or Commercial Spec.  If you buy the wrong type, it may prevent you from using the specific stock you wanted/bought.

If you intend to ever take off the flash hider to try other designs, get at least a 16" barrel.  Any shorter, and the muzzle device must be long enough to reach 16" and be pinned to make it legal.

I bought just the castle nut wrench initially because I didn't need the barrel wrench -- I bought a full upper with barrel already attached.  Second build, I bought the upper in parts.  When I shopped for a barrel nut wrench, I wound up getting one that also does castle nuts.  Should have gotten the combo wrench first!

Read all the reviews on bolt carrier groups before buying.  You don't need the most expensive, but sometimes the cheapest can be problematic.  #1 thing I look for is reduced friction.  The smoother the carrier, the less I worry about keeping it wet with oil.  Some reviews I see point out how they ordered that BCG because of the nice shiny finish, only to find the finish is rough and causes friction.

Free-floating the barrel is a major advantage for my builds at least.  improves accuracy, and allows a longer hand guard than those that stop at the gas block.  I also found free floating seems to mechanically zero the sights better than using an A2 front sight block.

As with anything, there are fine details.  Overlooking any of these won't mean your final build isn't going to perform well.  These are just hints to make the process smoother and hopefully avoid the pain of having to learn from experience!

Mahalo for all the tips!  Using the plastic tub to work in while installing the fiddly, spring-loaded parts sounds about like genius.   

Just ordered the upper and lower last night, so I'm on my way...

Don't mean to be technical,
but you're actually assembling an AR from parts.


Building an AR means starting from bar stock.



have fun. 

Don't mean to be technical,
but you're actually assembling an AR from parts.


Building an AR means starting from bar stock.



have fun. 

In a time when throwing a frozen Hot Pocket in the microwave without ruining it is considered "cooking" ...

we're "building" ARs!!

    

Don't mean to be technical,
but you're actually assembling an AR from parts.


Building an AR means starting from bar stock.



have fun. 

Exactly!  I've got a couple of aluminum blocks on the way, and new bits for my Dremel.  What could go wrong?

The lower's just about done.  The hammer had a little hitch in its getalong at first, but a little CLP and a few cycles smoothed it right out.  Took me a little while to figure out what the anti-rotation pins were...  Google knows all.

Things I've screwed up so far:
- One very small ding in the finish...  When in doubt, tape!
- Initially used the wrong spring for the selector lever.  The LPK came with a spare spring for pivot/takedown pins, and I dropped that in.  The lever felt sketchy as hell, lots of play and not the positive "click" I'm used to from GI M4s.  Found http://www.biggerhammer.net and the FAQ page with detailed dimensions of all the spring and pin sizes, which helped me realize I had the wrong spring.  Put the right one in, and it felt better, but still a little loose.
- It felt loose because I'd also used the wrong detent.  Once again, Google to the rescue...  There was also a spare detent for the pivot/takedown pins in the kit, and I'd put that in too.  Switched it for the right one, and now it feels just right...
- Lost the buffer retainer detent spring, because my workbench is a mess.  Luckily, I found a GI ballpoint pen that was willing to donate its spring for the cause...  Seems to be working so far.  I've got replacement springs on the way in case it starts to not work.

A couple more questions:

- Any recommendations for a good BCG for a reasonable price?  I'm not looking to drive tacks, but I'd like good practical accuracy and high reliability.
- I know that if I get a 14.5 inch barrel, I've got to permanently install something to bring the overall barrel length to at least 16 inches (e.g., a pinned flash hider).  Seems to me if I do that, I won't be able to take the gas block off later if the flash hider outer diameter is bigger than the barrel... right? 

Thanks for all the advice so far...  It's a lot of fun watching it take shape!   

yeap
your gas block will not slip off the barrel.

The AR is over engineered! Now doesn't the AK design solve all little springs and do dads.

That's what I thought, and so I guess I'll be going with a 16" barrel, 'cuz I like to tinker with stuff.   

The pins and other fiddly bits aren't TOO bad, as long as you know which goes where.  And a set of spark plug gappers works like a champ for keeping in the little potential high-speed projectiles. 

Never shot an AK...  might have to see if I can find one...

- I know that if I get a 14.5 inch barrel, I've got to permanently install something to bring the overall barrel length to at least 16 inches (e.g., a pinned flash hider).  Seems to me if I do that, I won't be able to take the gas block off later if the flash hider outer diameter is bigger than the barrel... right?

Yankee Hill makes a two piece gas block with a folding front sight. http://yhm.net/front-flip-sight-tower-standard.html I installed one on one of my builds ( a drop of purple loctite on each screw) and after a few thousand rounds it's never loosened... knocking on wood. They are available locally for less than ordering from YH.

Yankee Hill makes a two piece gas block with a folding front sight. http://yhm.net/front-flip-sight-tower-standard.html I installed one on one of my builds ( a drop of purple loctite on each screw) and after a few thousand rounds it's never loosened... knocking on wood. They are available locally for less than ordering from YH.

That would limit me to a pretty short hand guard, though...  Decisions, decisions!

If you plan to free float the barrel, just start with a low profile gas block.  I doubt you'll ever go back to anything else, so no worries with the pinned muzzle device.

If you aren't sure the muzzle device you pin is the perfect one for you, I'd recommend going with a 16" barrel.  Then you can mix and match handguards, gas blocks, front sights, and muzzle devices all you want! 

If this is a project gun, don't make it too difficult to swap parts.  You can always make the next build a shorter "clone" after you've identified which components are "you!"

Assembling ARs is great fun.

Main thing is to not go crazy spending money.

Figure out what kind of AR you want (be realistic in how you'll use it) and build just that. It's easy to go crazy.

Free float is great. I have 2 free floats, but regular hand guards work great and are my preference for shorter guns. People go a bit crazy and think every AR has to be about improving accuracy. My 16" with MOE hand guards is lightweight and fun to shoot. What more do you want?

First rounds through it today!  It didn't blow up, which I consider a win.  Accuracy was OK; probably some combination of operator error and the $35 reflex sight I put on it.

Functioned pretty well; no FTFs or FTEs, went "bang" every time it should have, didn't go full-auto.  One thing that concerned me a little was that on an empty mag, the BCG would lock, but not *all the way* back...  It would end up about an inch forward of full back.  Since I didn't have any FTFs, I figure it's cycling all the way; maybe my mag springs are weak?  I was using GI ten-rounders that are at least 25 years old...  One of them wouldn't lock the BCG at all.

Regardless, I had fun, and now I want to see what it can do with a decent scope...

didn't go full-auto.

Awww, that's too bad...