March 1, 2024

We all know that one guy with six different AR-15s, each only slightly different than the last. That guy is never going to run out of parts to keep his guns running—when he needs a new extractor or recoil spring, he can just cannibalize it from one of his many extras.

For the rest of us, with only a single rifle and maybe a backup in the safe, spare parts are a necessity. If you want to keep your go-to rifle going, you need to be prepared to swap out wear parts, replace lost detents or springs, and handle freak accidents that can occur when your round count reaches up to the tens of thousands.

Why Stock a Spare?

We could call it Murphy’s Law or quote the adage that “two is one, one is none,” but simply put, things happen. The more you use your rifle, the more wear and stress you put on its parts, and the more chances you create for something to happen.

That something isn’t always a catastrophic failure. Maybe it’s something as simple as your buffer spring retainer firing out during a disassembly. Technically, your rifle can function perfectly fine without it, but it’s awfully annoying to have your buffer try to launch out every time you split open your gun. This annoyance can be avoided by stocking a spare buffer retaining pin and spring, at less than the cost of a cup of coffee.

Why Stock a Spare

Spare parts provide cheap insurance to not only keep your rifle running but keep it running well.

The Most Important AR-15 Parts

We like to break spare parts down into 3 categories: consumables, just-in-case parts, and accident-prone parts. You can shop for all of these AR-15 parts incrementally, to spread the cost out over time.

The Most Important AR-15 Parts

Consumables are a class of parts that are very high wear. For these parts, it’s not a question of if they will fail or degrade, but when. If you want to keep your rifle running for thousands and thousands of rounds, you will need at least one spare for each of these parts eventually.

Just-in-case parts, our second category, is comprised of those parts that might last for ten thousand rounds or more but will render your gun inoperable if they don’t. These are optional, but any well-prepared gun owner would be wise to keep a few around.

Lastly, accident-prone parts are those like the aforementioned buffer retainer spring—parts that are easily lost or broken, not by wear from use, but by user error. These parts are optional. If you are utterly confident that you will never make a mistake and allow one of these parts to be lost or damaged, then you can safely omit them. But, in our experience, mistakes happen even to the most expert of gunsmiths, and given the minuscule cost of these parts, it’s better to be safe than sorry.

Consumable Spare Parts

For users concerned about the longevity of their rifles, we recommend keeping at least one of each of these parts. Those with particularly demanding firing schedules may go through several.

Some prefer to replace these parts on a regular schedule, typically every 2-5 thousand rounds, but others prefer to wait until the original parts exhibit issues before replacing them, to maximize their value. That choice is up to you, so long as you have the parts in hand when problems do crop up.

Magazines

Often overlooked when it comes to spare AR parts, magazines are one of the most important backup components you can stock.

Magazines

Anyone who has ever shot with worn-out magazine springs can attest to the utter frustration they cause. Bad magazines are capable of reducing even the most reliable AR-15s to frequent malfunctioning nightmares.

Technically, the only consumable part of the magazine is the spring—the follower, body, and floorplate will often outlive the rifle they’re used with. However, magazines are a cheap enough component that it’s usually worth buying a few complete spares, although stocking bare springs is an acceptable alternative for those on a budget.

Having complete spare magazines protects you not only against spring fatigue, but also against incidental damage from drops, getting stepped on, or any of the myriad of other things that can happen in the field.

Recoil Springs

Any spring that is repeatedly compressed and extended will eventually lose strength; it’s a simple fact of material science, and there’s no getting around it. All you can do is replace the spring once it’s worn.

Recoil springs are one of the most crucial. When this spring loses strength, you’ll know it, because your rifle will start to have issues with feeding and cycling, severely limiting its utility.

Recoil Springs

Recoil springs are often replaced every 5,000 rounds as a preventative measure to prevent issues from ever occurring, although some aftermarket springs claim service lives far more than that.

Fire Control Springs

Starting to see a pattern here? Like recoil and magazine springs, your fire control springs can grow weak over time, leading to light primer strikes. These tend to outlast recoil springs, but your experience may vary depending on factors like manufacturer and material.

Fire Control Springs

Extractors (And Their Springs)

Extractors are one of the more controversial items on our consumables list. While they can begin to fail as early as two thousand rounds, it’s also not uncommon for them to remain functional for ten thousand rounds or more.

Still, with such an inexpensive and crucial part, we choose to err on the side of caution and stock an extra or two. Should your extractor or springs begin to fail, the first symptom will usually be failures to eject, which, depending on the exact nature of the failure, can be troublesome to clear, especially under pressure.

Gas Rings

Gas Rings

Gas rings are often one of the fastest parts to wear out in an AR-15, particularly if the rifle is shot rapidly or suppressed. Luckily, they are also one of the cheapest parts to replace.

One common test to tell if your gas rings are still up to snuff is to place your bolt face down on a flat surface in its fully extended position. If the weight of the carrier overcomes the resistance of the rings and the carrier slides down, then your rings are ready to be replaced.

This test is more of a guideline than a rule, though, so if you’d prefer to run your rings until you start to see failures, that’s certainly an option.

Just-in-case Spare Parts

Unless your round count is reaching into five-digit territory, these are parts that you may need to replace, or you may not. The quality of your rifle will have some impact on your odds, but there’s also a degree of luck that really can’t be ignored. Even the finest rifles in the world experience broken bolts from time to time.

Of course, if you are putting tens of thousands of rounds downrange, then these parts are more than likely going to break or wear out at that point anyway—but by then, you’ll have spent so much on ammo that the cost of a few spare parts is just a drop in the bucket.

Bolts

A broken bolt is one of the most common catastrophic AR-15 failures, particularly in rifles that fire rounds with a larger rim than standard .223/5.56 ammunition. While still relatively rare and far from an eventuality, it’s seen often enough that we recommend stocking a spare bolt just in case.

Note that this does not mean an entire spare bolt carrier is required; the carrier itself rarely fails in any way, so all you need is a spare bolt, which can be had for a fraction of the price of an entire BCG.

Firing Pin

Similarly, it’s not at all unheard of for a firing pin to break. Usually, this doesn’t occur dramatically, such as the pin snapping somewhere along the shaft. Instead, it’s often pitting or fragmentation at the very tip, creating an irregular surface that can no longer ignite primers reliably.

Less commonly, firing pins made with substandard materials can mushroom on the tail end where they are struck by the hammer, leading to the same malfunction.

As with a spare bolt, a backup firing pin is cheap insurance in the event of a failure.

Cam Pin

Cam pins aren’t generally considered a wear part because they tend to hold up quite well against the abrasive forces and friction generated by sliding against the receiver. However, they do still break on occasion, not along the wear surfaces, but instead usually at the thin points around the opening in them where the firing pin sits.

Because of this (and because cam pins cost all of a few dollars), it’s worthwhile to have a spare or two around.

Barrel

Barrels don’t fit very neatly into either consumables or just-in-case parts, instead sort of straddling the two categories. Technically, they are consumable, since your barrel will eventually wear out and accuracy will degrade.

However, modern barrels fired at semi-automatic rates of fire often have such long lifespans that they rarely need replacing, sometimes exceeding ten thousand rounds. That kind of longevity is far from guaranteed, though, so we recommend stocking a spare barrel as part of your just-in-case parts, as a hedge against premature barrel wear. For faster calibers such as 6mm ARC, barrel life may be considerably shorter, and so a spare barrel is usually advisable. 

If you frequently mag-dump through your AR-15, consider moving this part to the consumables category.

Accident-Prone Spare Parts

While these parts don’t often break on their own, if you work on your rifle frequently, sooner or later you’re likely to launch a detent off into the ether. Sometimes they can be recovered—often not.

Because of how inexpensive and commonly lost they are, you’ll often see these parts bundled into an “oops” kit. The kit is comprised of all of the small detents and springs that are under pressure when an AR-15 is disassembled.

Accident-Prone Spare Parts

Here’s the list:

  • Takedown Pin Detent
  • Takedown Pin Detent Spring
  • Safety Selector Spring
  • Safety Selector Detent
  • Buffer Retainer Spring
  • Buffer Retainer Detent
  • Disconnector Spring

Some “oops” kits may also include trigger pins and roll pins. We don’t feel trigger pins are necessary—they’re not under spring pressure during disassembly, so even a modicum of caution is usually enough to prevent them from getting lost—and while roll pins are easy to damage if you are frequently removing and reinserting them, there’s not much reason to do so. You shouldn’t need to remove your bolt catch or trigger guard for maintenance, and the forward assist is seldom removed at all.

You may at some point need to remove your gas tube roll pin when replacing the tube, but you’ll generally want to replace the pin at the same time anyway.

Making the Most of Your Rifle: .22 Conversion Kits

If you want to make your rifle last as long as possible, one option to reduce wear is to consider a .22 conversion kit for training and plinking. These kits replace your existing bolt carrier group and magazine, allowing your .223/5.56 AR-15 to feed and fire .22LR ammunition.

Making the Most of Your Rifle: .22 Conversion Kits

Opting for a .22 conversion kit reduces the strain on your rifle considerably. Your gas rings, extractor, and all the other parts in your bolt carrier group are spared entirely since they are replaced. Meanwhile, the strain on your recoil spring and barrel is massively reduced, although rimfire ammunition does tend to deposit a lot of fouling, so you would be wise to clean your barrel more frequently.

Spare Uppers

It’s not uncommon for users with a propensity for preparedness to stock one or more complete AR-15 uppers as a backup in case of a parts failure. This method is effective, although not very cost-efficient. 

Having an entire spare upper ready to go in the event of a failure makes dealing with the majority of parts breakages fast and simple—just rip the old upper off your rifle, pop on the new one, and keep moving.

Spare Uppers

This is particularly advantageous for less common parts failures, such as a squib rupturing a barrel. Should such a thing occur, you may not have the time or tools to immediately disassemble your upper and install your spare barrel, but swapping in a spare upper receiver takes barely a minute. 

Unfortunately, a single spare upper will generally run you more than every other part on this list combined, meaning that it’s not always an option for those on a budget. But, stocking an extra upper or two comes with other tangential benefits as well, such as the ability to change calibers from standard .223/5.56 to something more exotic, like .458 SOCOM, .350 Legend, or 6.5 Grendel.

Conclusion

As the saying goes, take care of your rifle, and it will take care of you. AR-15s are one of the easiest designs of all time to work on, making both regular maintenance and infrequent repairs a breeze, but you do need to have the parts on hand to do so.

A small reserve of spare consumables along with some just-in-case parts and an oops kit will keep your rifle up and running for thousands of rounds—all at the cost of less than a case of ammo.