BLUF: Cheap/shady companies who try to awe the public with “better than milspec” rifles but don’t even stake their castle nuts haven’t even met the “milspec” threshold to begin with, and thus are lying to the consumer. “Crappy” basic Colts/BCMs from the factory meet all of these requirements and will run like sewing machines until your grandkids find them gathering dust in your attic.
The first thing to clarify is that “milspec” does not actually mean the lowest bidder. “Milspec” means the lowest bidder…. who meets the requirements set forth in the technical data package during the military procurement process/solicitation. What this means is that when salty vetbros are whining about how their Radical Firearms rifle is so much better than that “sh***y wobbly milspec colt M4” they got issued back in the ‘stan, they don’t actually know what they’re looking at, and their primary complaints are about the aesthetic quality of the gun.
The TDP/Technical Data Package, which is the more accurate term, and the maintenance and assembly procedures are laid out in the various 23&P level manuals that are commonly available online. Simple google TM 9-1005-319-23&P.
The 23&P lays out all of the specs, along with assembly and maintenance methods, but I’ll repeat offhand the ones I can remember from stem to stern.
The AR platform was initially designed as a rifle length system. The further you stray from any initial design, the less reliably that design will function without compensatory changes. This is reflected in other weapons as well, most notably the 1911. 1911s were designed as a full sized firearm, and “commander” length guns often introduce new problems that weren’t present in the initial format.
Starting from the rear, the “milspec” buffer tube is designed in such a way that it is significantly stronger than the commercial variant, with a smaller overall diameter but thicker sidewalls, and as such is more expensive to produce, hence the usual substitution on low grade guns. This added rigidity is quite simply more durable, and decreases the chances of a catastrophic failure should you fall on the gun, or clear a malfunction by “mortaring” out a round.
The castle nut, which secures the tube and end plate to the lower receiver, is supposed to be torqued to 38-42 FOOT lbs, (all torque values on an AR are ft lbs, sans accessory components), and then staked in two positions. If the castle nut cannot be staked, (such as the newer Daniel Defense guns), or if it has not been staked, or if it has not been torqued, or any combination therein, it is NOT a properly assembled component. If these things haven’t been done, there’s a good chance that your castle nut will eventually work loose mid string, creating an embarrassing malfunction on the range or a life ending malfunction in a real event. Some builders will forego staking in favor of using loctite or a similar product. This does not secure the components properly, and encouraged the buffer to rotate with the nut, potentially shearing the locking post and causing major issues.
(Above image pulled from INGunOwners forum)
The buffer within the tube should be at least an H, but preferably an H2 weight for any carbine or midlength system that is properly gassed. Cheap companies often use “carbine” or unmarked buffers which are lighter, because it saves them money on the filler tungsten. This will cause the action to cycle in a much more violent manner than originally intended by design, putting undue stress on the system, shortening the life of the bolt, potentially causing malfunctions, and creating extra recoil.
Some people get upset because their buffer “makes noise”, so they swap to gucci aftermarket “dead blow” buffers or any other such nonsense, this changes the mechanics of the action in such a way that you are negating any potential reliability advantage and shortening the life of the gun, or inducing malfunctions, or both. Hydraulic buffers or “silent capture” buffers are another favorite of the hobbyist, and introduce their own concerns, as well as additional failure points. Just stick to a normal H-H2 weight buffer and you’ll be safe.
Lower receivers are pretty hard to mess up, but the problem with overly cheap lowers is that they’ll have a lower amount of scrutiny in accepting the parts, which means they aren’t properly checking hole size or quality. Companies with low rates of part returns/DQs are often attempting to save money on production, as proper inspections take time and result in lower overall production numbers. This will give you a difficult to assemble lower at the best, or a non-functioning lower at the worst. If you must go for a cheap lower, stick with one that’s prebuilt so at least you have a guarantee that it will assemble in the first place.
Cheap companies also often use cheap LPKs, which can break or shatter at an abnormally low round count. Additionally, low-end companies will occasionally include trigger spring kits which are far too rough/heavy, in an attempt to guarantee ignition on cheap steel cased ammo, resulting in an overly heavy or gritty trigger. I recommend sticking to Schmid Tool produced LPKs, which can be identified by a stamped “S” on all the parts. This is what Colt uses, along with several other “duty grade” companies, and can be found sold separately by companies like Sionics.
Upper receivers must have the appropriate feed ramps for the barrel used. Either no ramps for a rifle, ramps for a carbine, or generally just in the proper configuration. The feed ramps on the barrel extension must match the feed ramps, (or lack thereof), incorporated into the upper. There’s a chart floating around that shows the acceptable combinations. Low end companies don’t care, because they’re buying parts cheap and throwing them together. Good companies will make sure these things are being confirmed.
Bolt carrier groups along with barrels are the heart of reliability. A proper bolt carrier group is both HPI and MP tested, and will be marked as such. Additionally, proper BCGs have definitive staking and GOOD fasteners on the gas key. If your gas key screws have “YFS” stamped on them, that means the company that assembled it couldn’t be bothered to spend an extra few pennies on good screws, and these parts will eventually fail given the opportunity, resulting in your gas key going askance mid shot and horribly binding the whole thing into a massive mess.
Cheap companies will also go out of their way to avoid taking the time to torque their barrel nuts. On a standard M4 barrel nut, the extension and threads should be slathered with Aeroshell 33MS grease, and then torqued to 35-70ft/lbs with a torque wrench after “seasoning” the threads. Seasoning is achieved by torquing the nut to spec, breaking it loose, retorquing and rebreaking 2-3 times. This “stretches” the threads and insures that they will hold the final torque value. This isn’t a totally necessary procedure, but it takes very little time and is a good practice.
If you don’t use Aeroshell on your receiver extension threads, you run the chance of sticking lithium grease on there, or no grease at all, and as the gun heats and cools you might create a battery-like reaction which will effectively weld the barrel to the gun. If you don’t care, fine, but I’ve shot out barrels before and being able to change them later on is an advantage. Additionally an improperly torqued barrel can result in poor accuracy, reliability, or both.
Cheap companies avoid all of that because it takes an extra few minutes to do, which means they have to slow production and push out less cheap guns. It’s an absurd practice, but they’re chasing the cheapest product to pad their bottom line and people buy those guns every minute, deterring them from changing their methods. Great for them, bad for you.
The barrel itself is held to material standards via the TDP, but that matters less for civilian shooters. Some barrel steels and coatings produce more accuracy, and civilian shooters don’t have the same durability requirements the .mil has, so that’s a wash. The important part of the barrel is the gas port.
Gas ports are held to specific standards based on the overall gassing configuration. The proper gas port sizes are available within the 23&P and other parts of the internet with minimal searching. Look for information published specifically by NSW Crane. Crappy companies will intentionally oversize gas ports so the guns will run steel cased ammo, along with cheaper underpowered loads. This leads to excess recoil, quicker gas port erosion, and expedited parts breakage. The gas system is a system, after all. It relies on proper porting, proper dwell time past the port in the guise of additional barrel length, and proper buffer weight. If any of these things stray from the TDP, your reliability and durability will suffer.
Gas port sizes are a crapshoot on cheap barrels because the average home builder has no way of confirming the size unless you’re also a machinist by trade and/or have calipers laying around. If you just spend the money on a known company, odds are you’ll be in good shape. Keep in mind that midlength guns do not have a NSW Crane approved port size as of the time of writing because middie guns haven’t yet been accepted for service, so a standard hasn’t been explored. That might happen before too long with some of the newer SOCOM variations attempting to come online.
Additionally, low-end companies are not always the best about aligning the port properly, or assembling the guns with properly aligned gas blocks. This will cause cycling issues, but you won’t be able to figure this out until you’re actively putting rounds through the gun. Going with a known-good company greatly reduces the chances of this occurring. If you receive an improperly drilled or mounted gas port/block, you might be dealing with a deadlined barrel from the start.
In closing, spend the money up front and buy at least one solid rifle from a known company, and save the cheaper builds as fun range toys afterwards.