Assembling an AR-15

[10-4]

I'm wondering about those members who have put together or built their own AR.  Did you end up with a reliable rifle?  I ask because as I understand, as long as the parts are made to the Mil Standard they'll fit and they're fully interchangeable.  It's most definitely less expensive to put one together vs purchasing one from a major manufacturer but I wonder what (if) the major manufacturer does to fine tune the rifle after assembly.  Search as I may I see no "adjustments" on these rifles.  The headspace is set and I don't see anyone measuring it or changing it.  The trigger is a drop-in unit and I don't see mention of stoning the parts. 

My AR (plain $699 S&W M&P 15) has been 100% reliable. 

If you've put one together did you find it to be 100% reliable?  If not, what specifically did you have to do to get it reliable?

I'm looking to purchase a lower receiver and then add all the parts and have a rifle I built from scratch with the parts I choose.  Is there any penalty to doing it this way?  I'd hate to put together a really nice rifle and then find it feeds poorly or fails to extract/eject. 

As far as forged lowers - is there any difference (besides appearance) between Company A and Company B forged Mil Spec lowers?

Thanks!

[sqlbullet]

I have two completed AR-15's in my safe.  An 18" SPR build and a 16" 300 blackout carbine build.  Both used Aero Precision Lowers and PSA (palmetto state armory) blemished uppers. Both used lower build kits from PSA with Magpul MOE pistol grips.

Beyond that they are quite different.  I have no issues with either of them, though I don't have but a couple hundred rounds through each.

I recently helped a friend assemble three AR's.  He is an AK guy and makes no bones that he bought them as a hedge against the next run on ar style rifles.  he intends to triple or better his money.  His all run fine.

As far as your questions.

1.  You can get a decent AR these days for about $500-$600 if you shop and aren't concerned about a "brand".

2.  You can build a much better AR than you can buy for the same money, or, you can build the same AR quite cheaply.

3.  Like Glocks, if the parts are to spec, and are designed to work together, they are legos.  They just go together.

3.5  It is recommended to check headspace with a set of gauges.  I personally always do.  Lots of guys don't.  I have never had a barrel/bolt combo fail.  If they do you can usually resolve the issue by playing musical bolts until you find one that works.  This is an advantage of buying your bolt/barrel from a local shop they caters to builders.  They will usually let you rummage through the bolt bin in the rare case your bolt and barrel won't headspace.  If buying online, you can buy a pair that the maker will check before they ship.  FYI, they headspace via the musical bolt method.

4. A mil-spec lower is a mil-spec lower.  Currently the best deal is on lowers from Anderson Mfg.  They are commonly found for $39.99 each, and you will see sales for $35.00 each.

Couple of comments that are relevant.

Know your feed ramps.  Upper receivers may or may not have M4 feed ramps.  Same goes for barrel extensions. Here is the summarized deal. 

Ideal combinations for feed ramps are non-M4 upper with non-M4 barrel OR M4 Upper with M4 barrel. 

Usually acceptable is a non-M4 upper with M4 barrel.  Most guys that have done this report no issues. 

An M4 upper with a non-M4 barrel will usually jam.  It creates a lip where the barrel extension meets the feed ramps cut in the upper that catches bullet tips.  It can be resolved usually with a chainsaw file, but unless you are both broke and already have parts, just buy or replace to end up with matched barrel and upper feed ramps.

Unless you have a specific reason not to, just get an upper with M4 ramps and a barrel with M4 ramps.  They are the most common so if you just order blindly that is what you will get.

There is a trigger job for the military type triggers that some guys (me) will do.  It does involve polishing the sear and sear hooks.  No stoning though.  The hardening on these parts is very thin, to beyond a very light polish and you will just ruin them.  This budget trigger job also involves working over one of the hammer spring legs.   I did this to one of my AR's, but not the other.  After several thousand dry-fires, I can't tell the difference between the two.  The trigger is OK, but not a match trigger.  If that is your goal, ante up to Timney or Giselle. 

HPT/MPI.  Know them, love them.  This usually matters for bolts, but also is done to the better barrels.  HPT is high pressure test, and MPI is magnetic particle inspection.  If you go to PSA you will see they have cheap bolts that are neither HTP or MPI.  For about 20% more you will find bolts marked HPT/MPI.  The difference is price is the cost of the test, which is small, and the cost of the failed bolts, which is about 1 in 10.  Just because 10% of the bolts failed the test doesn't mean they will fail in use in your gun.  I generally wait for a sale and get HTP/MPI.

Occasionally you will see bolts marked MPI, but not HPT.  IMHO this is no better than a bolt that isn't marked.  The purpose of the MPI is to find cracks caused by the HPT.  While the occasional bolt will fail MPI alone, the tests are really meant to go together.

I could keep going, but I think that covers the basics.  If you are serious about building, it is really worthwhile to get a book.  I bought "Gunsmithing the AR-15" by Sweeney.  I found it worthwhile and informative, and a negligible increase.

Final word of caution.  This is addictive.  I now have 9 AR-15 lowers waiting on builds, and 3  AR-10 lowers waiting.  I have a barrel on my desk right in front of me (had to move it to start this post) and two more on the way.  Good luck to you and your bank account.

[Pablo]

Not much I can add to sql bullet's excellent post. He more than touched on the trigger. I guess I'm a little odd or picky, or learned from my first AR purchase. I really just don't like the stock GI trigger, so don't buy the parts kits with all the trigger parts and waste time installing only to take it back apart. My favorite is the POF Trigger on sale (regular price is crazy and no need ever to pay $199).

ANNNND I really hate those cheapie parts kits. Junk stuff, IMHO. Rough nasty pins, sharp burred detent pins, crap asss metallurgy springs. Expensive I guess to buy the good stuff somewhat individually, but if you want a rifle or two to be distinguished, worth it IMHO.

I bought my first AR a DD. EXCELLENT AR. I have built since. 5.56, 6.8SPC, 10mm.

[10-4]

Thanks for the replies!  Good information, and reassuring.  Now, I've already "upgraded" parts of my S&W M&P AR-15 which resulted in my having a box full of perfectly good parts so I figured why not build an AR.  The first thing I upgraded was the trigger - I didn't like the stock trigger (at all) so I added a Timney Trigger.  Then I swapped out the bolt and carrier with JP Precision parts which seem much smoother and are made from a different material.  No mag particle inspection or high pressure test references but I believe that's because it's a different material.  I've written the company to find out what's up.

Then I changed out the charging handle because - because (as my dear old dad would have said) I had $60 burning a hole in my pocket.  And then I added an EO Tech holographic sight and the 3X multiplier. 

So, it's time to get a book, a lower, and start building my personalized AR.  Since the S&W is a carbine I figured I'd build a longer rifle for longer distance shooting, maybe 18" or 20", with a rifle length gas system and a high quality barrel.  And a scope.  And I still want a .308 rifle so that will be my second build. 

This is fun.  And as of today it's still legal in the USA. 

[sqlbullet]

My spr build has a Rainier Arms barrel that set me back 3 bills.  I just ordered a 20" Anderson barrel for $125 that I have read good reports on.  It will go in my service rifle build until I get enough better to justify a different barrel.

[will965]

can't go wrong with a Rock River two-stage match trigger. I put those in almost all of mine it's not super expensive and they are crisp and clean. Also when building an AR it's all about the barrel....

[sqlbullet]

Also when building an AR it's all about the barrel....

This.

But keep in mind that even cheap AR barrels shoot better than 95% of shooters.  It will take me a good while to even get close to the capabilities of my match barrel.

[10-4]

https://www.rainierarms.com/bolt-jp-enterprises-inc-enhanced-bolt-223

This is the bolt I mentioned.  Different material and no mention of nondestructive testing or pressure proofing. 

[sqlbullet]

JP Enterprises will stand behind their product.

A further comment about mil-spec.  Doesn't mean best.  Means built to a certain spec.  They are an interesting read if you are bored.  There are better options for most parts, but they aren't mil spec.

[Ramjet]

Built two so far lowers are DPMS cost me less than $50.00/each.

One is married to an upper built from YHM parts and chambered for the 6.8....MOA gun through and through. Furniture on the gun is Magpul.

The second is a 458 SOCOM RRA upper married to the DPMS lower built up with quality parts from Magpul and other High quality parts. This gun is sub MOA out to 200 yards.

Both guns have Trigicon optics atop.

[will965]

Ramjet,
I am dying for a 458 socom upper ....

[Pablo]

Ramjet,
I am dying for a 458 socom upper ....

Me three.

[Ramjet]

Rock River Arms I have is an outstanding upper and might be one of the most accurate rifles I own. I have the Hunter Muzzle Brake and the heavy barrel. I will snap a pic tomorrow and post it.

[will965]

And to the op, built several with rock river receivers,  colt uppers,PSA stuff, all super reliable... Quality parts make for a nice rifle.

[sqlbullet]

For reference here are the parts lists in my two current completed builds:

SPR:



Lower
Aero Precision lower
Palmetto State Armory lower build Kit (MOE)
Tactical Intent Mil-Spec receiver extension/buffer kit ($49.95 Amazon)(
Fab Defense Mako Stealth GL mil-spec stock ($105.65 Amazon)

Upper
Palmetto State Armory blem upper
PSA Premium Full Auto BCG
Forward Assist Kit ($21.65 Amazon)
PSA Ejection Port Cover Assembly
Tactical Intent Charging Handle ($25.95 Amazon)
Rainier Arms UltraMatch 223 Wylde 18 SPR
Stainless A2 Style birdcage
DPMS micro .750" gas block ($18.99 Amazon)
Veriforce Tactical rifle gas tube w/roll pin ($13.99 Amazon)
Model 1 Free Float Tube ($35.00 Midway)
UTG AccuShot Picatinny/Weaver Medium Profile 2-piece 1-inch Rings ($10.27 Amazon)
Bushnell Elite 3200 10X40 Mil-Dot ($189.99 Midway)

300 AAC Blackout



Lower
Aero Precision lower
Palmetto State Armory lower build Kit (MOE)
Tactical Intent Mil-Spec receiver extension/buffer kit ($49.95 Amazon)(
OT Supplier T6 six-position buttstock ($30.99 Amazon)

Upper
Palmetto State Armory blem upper
PSA Full Auto BCG
Forward Assist Kit ($21.65 Amazon)
PSA Ejection Port Cover Assembly
Tactical Intent Charging Handle ($25.95 Amazon)
CMMG 16" 300 AAC Blackout carbine length
Rousch Premium Tactical 10/15 A2 Bird Cage .308 ($13.50 Amazon)
SAS products low profile gas block .750" ($9.40 Amazon)
Veriforce Tactical carbine gas tube w/roll pin ($6.99 Amazon)
Leapers UTG PRO 4/15 Super Slim free float handguard ($137.50 Amazon)
GDT Front/Rear 45° BUIS ($19.35 Amazon)
UTG Max Strength LE Grade Quick Detach Picatinny Scope Rings ($22.92 Amazon)
NC Star Long Eye Relief 4X scope

I am quite certain I could build them 10-20% cheaper today, just because parts have come down in price.  For instance, those lowers cost me $59 each, but today I could get a two pack from anderson for $70.  And I would probably be just as happy with a Ballistics Advantage barrel in my SPR build at about half the price.  I was also surprised at how many incidental parts I got on Amazon that have worked just fine.