Rifle Ergonomics: Optimizing Your AR Setup

Primary Arms Staff

1/27/2020 1:07 pmwww.primaryarms.com

AR 15 Ergonomics


an applied science concerned with designing and arranging things people use so that the people and things interact most efficiently and effectively.


Even with a clear definition, few words are misused so frequently. You may hear infomercials tout it with impunity: ‘This duster broom is so ergonomic!’ or ‘Ergonomic phone case fits in your pocket!’ After a while, the word seems to lose meaning. In the end, even a brick is ‘ergonomic’ when compared to a cinderblock, right?


Despite the confusion, ergonomics is a powerful word. When we talk about AR10s and AR15s, ergonomics come first.


Unlike a phone or a broom, a rifle’s ‘efficiency’ and ‘safety’ are critically intertwined. The history of the AR15 (and its resulting prevalence) lends itself entirely to the rifle’s unparalleled ergonomics. By no exaggeration, the AR15 is such an intuitive design that it became the gold standard for modern rifles.


Whenever new designs step forth, experts ask the same question: how is it better than an AR? How does it make the user more effective? Are its controls as clear and simple? Is it safer to use in harsh conditions? These are important questions, and they all stem from that core concept of ergonomics: optimizing for both efficiency and safety.


Optimization doesn’t come in a vacuum though. There is no perfect rifle for every job, and your rifle’s setup will either help or hinder when put to the test. Every component affects your rifle’s operating efficiency, and some choices are more subtle than others. Weight, size, and caliber are major contributors, but that vital minutia can go unnoticed.


With all these considerations, how do we know what’s ‘ergonomic’?



The Key to Rifle Ergonomics


The first step of an efficient build: establishing purpose.


Rifles are purpose-built machines, configured to a specific role for the best possible performance. Every part you choose contributes to this overall purpose, driving your AR into a specialized niche. For example, if a builder purchases an 11.5” lightweight barrel, they’re prioritizing close-quarters maneuverability and speed over long-distance precision. The purpose of their rifle could be described as close-quarters self-defense. On the other hand, if a builder buys a 20” heavyweight barrel for their AR10, they’ve forgone maneuverability for superior performance at further ranges. In this case, the purpose might be long-range benchrest target shooting. Every part will feed into purpose, even if that purpose is purely aesthetic.




When considering ‘ergonomics’, we judge parts based on their efficiency and safety as it relates to our build’s intended purpose. Much of this comes from understanding a part’s features and benefits. Some parts will have very specific feature sets, clearly designed for peak performance in one application. Other parts will be more generalized and differ only slightly from its alternatives. As the purpose of a rifle becomes more specific, the part selection will become more limited.


By approaching ergonomics with this purpose-first mindset, we can establish criteria of comparison and rank them by importance. Weight, size, and price are all important criteria in any build, but everyone will have their own priorities.



Getting Started


When you’re planning your build, think big and narrow down.


What caliber should I use?


Most builds start with a caliber. Because AR15s and AR10s have become standard, you can find a build in almost any caliber on the market. Every caliber has advantages and disadvantages, so if you know your rifle’s purpose, you’ll want to optimize your chambering. Common intermediate calibers like 5.56, .300blk and .224 Valkyrie may look similar from the outside, but their performance varies greatly.




Research the unique benefits of each cartridge, compare them based on your criteria, and select the one that best fits your demands. There are no perfect cartridges though, so remember that some compromises are inevitable.


What barrel length should I choose?

Your best barrel length will depend on caliber. If you are building a .308 with the purpose of long-range precision, a 20” barrel makes more sense than an 11”, as the 20” barrel achieves higher muzzle velocities for flatter trajectory. If you want an AR pistol for home defense, and you’ve chosen 5.56 for your caliber, you may lean towards a 10.5” barrel for enhanced mobility in tight corridors.


Barrel length, ballistics, and maneuverability maintain a complex relationship, but the basic relationship is simple: long barrel for long-range, short barrel for short-range.


How much should my rifle weigh?


Weight is a major factor in ergonomics, and many builders forget about it until the very end. Lightweight rifles are easier to manipulate and reduce muscle fatigue, but overall balance is equally important. A nose-heavy rifle recoils less, but the added weight makes it harder to point. A rear-heavy rifle is quick to point but may drift more with each shot. Most builders balance their rifles over the magwell for a consistent middle-ground.



Kitting Out


Once you’ve chosen your rifle’s overall profile, you can make decisions on key components like your handguard and furniture.


Most standard MIL-SPEC AR15 receivers will perform similarly, though you can fine-tune your controls with some specialized small parts. If you want non-standard, lightweight billet receiver sets refine your rifle with meaningful weight savings, while ambidextrous receivers can streamline your southpaw marksmanship. If you’re thinking ambi, take a look at the LMT MARS receivers. They are truly ambidextrous and feature the unmistakable quality of LMT’s machining.



Best Handguards

The handguard debate is a well-tread path.

Handguards are our forward connection to the rifle, acting as the first line support for the muzzle. Slim handguards with M-LOK or KeyMod attachment are thinner and weigh less than a Quad Rail, but Quad Rails are exceptionally durable and offer the most flexibility for accessory positioning. Of course, there are so many options available nowadays, every generality has an exception. That’s why you should evaluate each product case-by-case.



Handguard length depends both on barrel length and user preference. A longer handguard will offer more forward control at the cost of weight. If your barrel features a fixed front sight post, you’ll need a rail specially made for a front sight post.



Best Stock


If anything, your stock is just as important as your handguard. Stocks have two points of contact between your shoulder and cheek, and stock length affects length-of-pull. Picking the right stock for your purpose can be daunting, though, as there are countless options. For AR15s and AR10s, stocks come in the fixed or collapsible varieties, with fixed being more common on full-length rifles, and collapsible being common on carbines.




Fixed stocks excel when you’re looking for consistency and precision. Most fixed stocks are tailored more towards SPR and DMR builds, packaged with adjustable cheek risers and buttpads. This helps you establish a consistent length-of-pull and eye position for magnified optics, but it adds a good deal of weight to the rifle.


Collapsible stocks are the generalist option, offering great versatility for any rifle build. What they lack in stability, they make up for in adaptability. A collapsible stock is crucial when moving in and out of vehicles, firing from awkward positions, or taking tight hallways. Collapsible stocks are also great for use with body armor, as you can shorten the pull to compensate for plate thickness.


When it comes to top brands, Magpul is usually head of the list. Magpul has an incredibly diverse offering of stocks, including the SL-S, CTR, PRS and UBR. There are so many Magpul options, it’s difficult to even list all the configurations. B5 Systems and Mission First Tactical are also top picks with their storage-rich SOPMOD and Minimalist Battlelink stocks.




Pistols are limited to braces, but the SBA3 and new SBA4 braces are effective alternatives.


Best Pistol Grips


Your pistol grip is the last direct point of contact. Your trigger-pull and elbow alignment depend on the grip’s curves, and everyone has different preferences based on their hand size.


While some objective analysis is possible, your preferred grip will probably come by opinion. There are some basic rules though. A fully supported precision rifle grip with a palm shelf will be too bulky for room-clearing, where shallow angle grips like the Magpul K2 and B5 Type 23 P-Grip shine. Rubber molded grips, such Ergo or Hogue grips, can provide a contoured swell for a full-feeling hold without any excessive weight.


The best approach to grip choice is growing your experience pool. Feel as many different ARs as you can and note which grips felt the best. While it may not be as scientific, you’ll end up with something you know to be comfortable.



Attachments and Placement


Attachments are the secret spice of ergonomics. Depending on the rifle setup, you may have a few pounds in attachments alone. Nightfighting setups are particularly susceptible to bloat, as the user needs instant access to an IR laser, illuminator, and white light with their forward hand.


Rigging such a setup is easier said than done, especially when working with limited rail space. All those tools add weight to the nose of the gun, and when you add a suppressor, a previously balanced rifle can feel like an anchor. Accessory selection is a constant process, but we’ve gathered a few key point.


When looking at contact points, your foregrip choice matters. We recently wrote an article detailing the subtle differences between the different foregrip types. Foregrips can substantially alter your manual-of-arms, shifting your wrist angles to provide better leverage against recoil. They also change the way you interact with forward accessories, as your thumb lands higher on the rail. Every foregrip has its own unique cost and benefit.




If you’re setting up a defensive carbine, your flashlight should be a high priority, as the night is dark and full of terrors. You shouldn’t have to change your grip much to activate your light. Place it on a strong location like the 3 or 9 o’clock or add an offset mount for a convenient 1:30/10:30 hold. If you are planning a nightvision setup, you’ll need clearance for an IR illuminator and laser. In this case, a dual tapeswitch from Surefire goes a long way.




Finally, your optics choice should always be purpose-driven. Most folks know the difference between red dots, prisms, and rifle scopes. That subject is a bit too large to include in this article, but we can focus on one of the newest developments. Recently, many professionals have been drawn to extended-height mounts, and the rationale is compelling. Using a riser like Unity Tactical’s FAST system, you can bring red dot and holographic sights into a natural eye position for improved speed on target.





Concluding Thoughts


Ergonomics is all about efficiency. The key to efficiency is selecting a parts list conducive to your rifle’s intended purpose. Whether it’s competition, hunting, or personal defense, there are countless configurations that excel in their own specialized niches.


If you establish a clear purpose, set your criteria, and prioritize needs, you’ll find that selecting the right parts can be easy, even on a strict budget. We’re fortunate to be in the middle of a golden age for firearms parts. There’s never been a better time to start building, and the industry is as diverse as craft beer.


Building will always be a learning process. In your journey, you may find parts that just click, making everything feel easier. It’s a rare occasion, but an exciting one nonetheless. Just remember: if it compromises safety, it’s a no-go. Split times are never worth a hospital visit.