Things I learned building this AR

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BSA1

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Things I learned when building this AR or What YouTube videos do not cover.

Over the Christmas and New Years holiday season the bad weather and events cause me to retreat into the mancave. In doing so I finally managed to complete two AR projects. This particular AR turned out to be very challenging, informative and rewarding experience.

Now for the details;

For the Lower Assembly I used a Anderson closed trigger guard lower. I installed a heavy duty carbine buffer tube (7075 Aluminum), Mission First Tactical Minimalist Stock, Mission First Tactical grip, ALG ACT trigger and hammer and a lightweight bolt catch. I choose the MFT Stock and Grip to save weight. Assembly was straightforward and I had no problems.

For the BCG I choose a AERO Precision Black Nitride. Well made and high quality. No complaints.

So far so good but the Upper turned out to be a big challenge.

For the Upper I choose a Anderson smooth side Upper for a couple reasons. The first one is I believe the Forward Assist and Ejection Port Cover are unnecessary and the second reason was to save weight. I installed the barrel to the Upper and when I tried to attach it to the Lower it didn’t fit. The Pivot Pin fit fine but the Takedown Pin would only push partway in and I had to use a rubber tip hammer to drive it all of the way through the opposite side of the Lower. Ok I will reverse the assembly order by attaching it with the Takedown Pin first. No problem with the Takedown Pin but now the Pivot Pin would only push partway in so I had to reach for my trusty rubber tip hammer to drive it all the way home.

Hummm, not good at all. Fortunately I had another Anderson smooth side lower which fits the Pivot and Takedown Pins perfectly.

*builders note; check fit of Upper and Lower Receivers before starting assembly.

With that problem solved I moved on to the barrel. Since I was using a 15”
Free Float handguard I installed a CMMG gas tube. It took a lot of gentle tapping with a brass punch and my trusty rubber tip hammer to get it on. The good news is that sucker ain’t ever going to move. The set screws are just for looks.

With the Upper Receiver and Gas Block taken care of all that was left as to attach the barrel to the Lower. Or rather I tried to. I was using a 15” Free Float handguard with a rail that required the barrel nut be perfectly aligned with the Lower.

No go. Fortunately Brownells carries a barrel shim kit that has three different sizes of shims. With the shim kit on hand all I had to do was to mix and match the different sizes to get the barrel nut properly aligned.

Except how to get the shims on the barrel with removing the barrel nut and gas block. Remember how I said that the gas block ain’t going to move? After some long thinking it occurred to me that I could cut the shims and slip them onto the barrel behind the barrel nut. Aha! A pair of snips and a little mixing and matching of shims resulted in a perfect fit.

*builders note; do not install the gas block until after the barrel and barrel nut are checked for proper fit on the Lower.

With that problem solved all that was left was attaching the Free Float handguard and a A2 Flash Hider. For sights I am using SIG Romeo5 Red Dot.

The only remaining bad news is we have received a lot of rain, ice and snow and the range is too muddy to do any shooting. However the gun passed a function test in my back yard killing waterfilled Zombie water jugs.

I want to give a big shout-out to @GunnyUSMC for his help. I learned a lot and am very happy with the final result.

Now for some pictures;
 
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I would have to say, a very nice looking AR.
That's a looker! Love the backdrop too. The pre installed gas block has bit me before too. You figure out the proper order after a few builds and then they fly together.

Agreed, it IS a good looking rifle, should be a blast to shoot too.

The one i seem to do at least once every two or three builds, is time the muzzle device, and forget to put the gas block on before doing it.
Dry fitting all the major components is usually a good idea also. Its easy enough to get any scuffs off and return stuff thats out of spec before actually getting started on the build....ALSO advice I should have taken, and ignored a few times....
 
*builders note; check fit of Upper and Lower Receivers before starting assembly.

Nice looking rifle, but my "builder's takeaway" from your story is that Anderson made a lower that was out of spec. If I mixed manufacturer's of upper's and lowers, I might not be surprised (well I should be because I've got several mixed AR's that work just fine) but to mate an Anderson upper and lower and have it not fit, that's double not good.

Doesn't matter for me because I've only used one Anderson lower and won't buy another. It turns out that I don't like that the selector position isn't marked on both sides of the lower (at least it wasn't on the one I bought). Since I switch my selectors to the right (I'm a leftie) I can't tell what position they're in without looking at the left side and marking the selector on that side with a pointer marking.
 
Very nice! Any idea as to weight?

Not as it is now.

I weighed all of the unassembled parts, the packaging some of the parts were still in and the cardboard box everything was in a while back and it came out to a few ounces over six pounds. However since that time I changed some parts around such the free float handguard and sights.
 
Nice looking rifle, but my "builder's takeaway" from your story is that Anderson made a lower that was out of spec. If I mixed manufacturer's of upper's and lowers, I might not be surprised (well I should be because I've got several mixed AR's that work just fine) but to mate an Anderson upper and lower and have it not fit, that's double not.

I considered that but I think it is unlikely.

First of all as I am using a Anderson Upper and a Anderson Lower there is no mixing and matching.

The second reason is the other Anderson Upper I used fits perfectly.

This is my fifth Anderson Lower and all of them have been problem free. It doesn’t mean that this one isn’t a little out of spec. Anderson has the upper I sent them so I will see what they say. Either way one of them is slightly out of spec.
 
Congratulations on getting it done and overcoming a few obstacles along the way. It’s always nice to have Gunny’s arsenal available for inspiration and his guidance if need be on what works.

While I confess to having drooled over a few of the more distinct upper/lower receivers out there I have also been very content with Anderson’s quality and have plans for one next week as my daughter’s parts arrive.
 
Nice AR, enjoy it. The builder's lessons I learned first were

Pick a hand guard with anti-rotation tabs of some kind
and
don't bother trying to crank down the barrel or muzzle device without a good vice and block/reaction rod.

The big takeaway from your story, which is something I harp on EVERYWHERE that inexpensive AR lowers are denigrated, is to CALL THE COMPANY who made the out-of-spec lower. Anderson and PSA make their bones selling basic mil-spec stuff - it isn't any better or worse than any other company making the same thing, but because it's inexpensive people assume you're stuck with an OOS paper weight if there's something wrong. That's simply not the case, with ANY brand. If it's OOS, they'll fix it or replace it.
 
Update: The Lower was not out of spec. The Upper was. I received the replacement Upper and it dropped right into Lower for a perfect fit.

I was able to get to the range for a short function test and to zero the Red Dot sight. Everything works fine although I have problems with only have a Red Sight on the gun as I do not trust batteries. My LGS has UTG low profile flip-up sights. They are made in Taiwan but seem to have a good reputation on YouTube. Best thing is their low cost since the sights are there to only ease my worry about the Red Dot battery dieing on me.
 
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Very nice! Love to see a range report, I took my first build out last Sunday, boy was that fun. What red dot did you choose?
 
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Except how to get the shims on the barrel with removing the barrel nut and gas block. Remember how I said that the gas block ain’t going to move? After some long thinking it occurred to me that I could cut the shims and slip them onto the barrel behind the barrel nut.

Bad practice described here.

Barrel shims must be cut to be installed, but they should NOT be on the gas block side of the barrel extension shoulder. Shims should be installed between the shoulder and the receiver. Putting them on the gas block side runs the risk of rolling, wrinkling, and otherwise displacing or distorting the shim as the barrel nut is tightened over the shoulder.

Shims should be on the receiver side of the extension flange, so the gas block is never in the way. It’s the alignment pin in the barrel extension which forces us to cut the shim for installation.
 
Hummm. I wondered about that. Wouldn’t installing the shims between then shoulder and receiver change the headspace? I only used two .001”’shims. When I tightened the barrel nut I watched for signs that the shims were being distorted. Well I learned so more about the gun. Thank you for the advice.
 
Wouldn’t installing the shims between then shoulder and receiver change the headspace?

No. This is another a fundamental misunderstanding of the AR design.

Headspace is controlled by the interaction between the bolt and the barrel extension. Adding shims behind the shoulder as they should be does not influence that interaction in anyway. The forward travel of the bolt is stopped by the barrel tenon and the cartridge. The forward travel of the carrier is not halted by the rear face of the barrel extension or the interior wall of the receiver, but rather by the cam pin and the bolt. There is no way for barrel shims to influence headspace or lockup.
 
Did you lap the receiver before installing the barrel? Guess I should ask If you did it the second time, after finding that the upper was out of spec.

It also helps to know that the upper is squared off. Plus it can help you fine tune the torquing of the barrel.
 
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