The accurate AR

I recently had a discussion with a former gun blogger who has a readership about AR lower receivers, and specifically Anderson lower receivers. He was amazed that they were going for 30 dollars currently in the “gun glut” of all the firearms manufacturers ramping up for a Hillary win.

He was also dead set against them as they might not be “milspec” and pointed to a builder in Michigan who experienced tight mags not dropping free (USGI mags dropped free but not PMags) as his evidence supporting his opinion. Later he said that spending the money on a quality lower and a barrel was where he would put his money since “everything bolts to the lower” and the barrel is key to accuracy.

For full disclosure, I’ve done three builds on Anderson lower recievers, and find them to be as good as Mega or Aero Precision. I’ve also experienced the “magazines won’t fall free” with brand new issue rifles, so I don’t consider that a problem. The lowers will “break in” over time with use, or you can polish them if you want.

But in truth, he’s half right, the barrel is a great place to spend money for an accurate AR. He’s wrong about the lower receiver, as far as accuracy goes it only serves to hold the upper into alignment with the trigger and recoil tube while ensuring the magazine is positioned to continue feeding the upper, and if any of those dimensions are off you’ll know it straight away. This is why putting a White Oak or Compass Lake upper on top of any old A2 lower receiver with a decent trigger will produce match winning performance in the hands of a High Master shooter.

The upper receiver is where all the mechanical accuracy resides, and to build an accurate upper receiver you need a good barrel and a free float setup. I’ve used a lot of NM service rifle style free float tubes, which are a three piece affair, and I honestly think that the two piece “tube” style are easier to install for just as good results for accuracy. If you really want to you can true up the upper receiver extension shoulder, but honestly that doesn’t do much.

The barrel assembly needs to be manufactured correctly. The bore needs to be concentric with the external contour, and the chamber needs to be cut concentric to the bore. The barrel extension, where the bolt engages, needs to be installed concentric to the chamber and bore, and finally the gas port needs to be properly drilled at the 12 o’clock position. All of these are precision machining functions, and unless you have a machine shop in your garage and the skills to turn a blank into a finished assembly, you should just buy a quality assembly. Whether the barrel is cut rifled or button rifled isn’t something you’ll be able to tell on the target as long as it was done right.

I recommend Krieger, Criterion, Wilson, and Douglas although I’ve also had excellent accuracy from Colt and Bushmaster (and wouldn’t hesitate to recommend a Rock River either). I’ve purchased some actual Anderson nitrided barreled assemblies but haven’t run them through their paces yet, and for what I paid for them (less than a hundred dollars per) I’ll be ecstatic if they’ll perform consistently in the 1.0 to 1.2 MOA range with decent handloads.

If you are trying to save some coin by assembling yourself, feel free to use whatever lower receiver you want, as branding doesn’t show up on the target. But, like almost all things with a variable factory output based on variable market demand, you are more likely to get a lemon in times of massive production than in times of limited production. All the AR parts manufacturers will put out a dud here and there, so don’t get bent around the axle over internet reports of tight magazines or tight trigger pins, just buy the parts you need from a vendor with a good return policy, and perform your build as soon as you can so you can identify whether everything is going together or not.


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