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A high-quality AR-15 rifle should last you for years. But it’s a good idea to have some spare parts in the toolbox to keep your rifle in good working condition. These can range from simple pins and springs to complete assemblies—whatever’s necessary to keep your rifle firing.
Importance of Spare Parts
No matter how ruggedly built and reliable in operation, firearms are machines composed of parts subject to stress. AR-15 parts can wear out, break, or become lost. Loss often occurs when you’re building a rifle or disassembling your rifle for routine maintenance. However, some parts are also more susceptible to breakage than others. Consequently, it’s worth keeping spare parts readily available.
Spare Parts to Keep Handy
If you own an AR-15, it’s worth buying spare parts and assemblies to keep your rifle operational—these range from the mundane to the elaborate.
Springs are critical to the function of small arms, and the AR-15 is no exception. Coil springs are used for everything from driving the hammer forward to cycling the action.
As springs compress, their height can gradually shorten, reducing the power they can transmit, compromising performance. In the case of the hammer spring, if it becomes too weak, you may begin to experience light primer strikes.
Springs under tension also pose a risk of loss, so it’s worth having spares for this reason alone. Consider buying a spring kit for your AR-15 rifle.
Pins — retaining pins, cam pins, detents, etc. — can break. However, what’s more likely to occur is that you’ll lose one or more pins during field or detail stripping. The best insurance policy is for you to lay in a supply of spares. You should keep spares for every pin that is small enough to be lost.
The bolt is one of the parts that bear the most stress. Its locking lugs are resisting a significant amount of breech pressure — more than 55,000 psi (pounds per square inch) — every time you fire a round. If you fire thousands of rounds through your AR-15 due to your participation in fire-intensive training courses or competitive shooting sports, having a spare bolt, complete and properly headspaced, can be vital to continued operation.
Bolts typically break by cracking along the cam-pin hole or the slot for the extractor. If your rifle has a high round count, you should periodically inspect your bolt for cracks or other damage and replace it when necessary.
The extractor snaps over the cartridge’s rim when seated in the chamber, withdrawing it as the gas drives the bolt carrier group rearward. Extractors can crack, chip, or break, depending on the type of ammunition you’re using and the status of your rifle’s gas system.
A broken extractor or extractor spring is one of the primary causes, not surprisingly, of failures to extract. This is one of the parts most likely to break during extended firing sessions, so keep a spare extractor, extractor spring, and extractor retaining pin (see pins).
The firing pin rarely needs replacement, but if you’re unfortunate enough to experience a pierced primer, the firing pin can become damaged. As with other small parts, it’s possible that the firing pin could be lost during disassembly. The firing pin retaining pin is also subject to wear.
If the gas key is correctly staked and torqued, the bolt carrier will probably not need replacement. However, you may consider keeping a complete bolt carrier group on hand. If you experience cycling irregularities or stoppages, swap out one BCG for another. This can save time, especially during fast-paced rifle courses or matches.
If you don’t have a magazine, your AR-15 is a single-shot rifle. While not strictly a part, magazines can fail or malfunction — e.g., lips can bend, walls can deform. The magazine is also one of the most common sources of failure to feed. In addition to a hedge against failure, spare magazines also allow you to keep your rifle in action longer—lay in a few extras.
The Stoner system uses a tube to feed propellant gases from the bore to the bolt carrier group, where it expands inside a chamber formed between the bolt and bolt carrier. This forces the carrier rearward to unlock and cycle the action.
The gas tube can wear out, affecting the gas seal in the bolt carrier key, but this doesn’t happen that often. Still, it’s worth having a replacement, especially if you fire your rifle extensively.
Although a complete bolt or bolt carrier group will have a set of gas rings, having spare rings is also good practice. The rings seal the gap between the bolt and bolt carrier and can also remove fouling from the inside diameter of the carrier.
As the gas rings wear out, the seal degrades. When the rings no longer resist the forward movement of the carrier, which you can test by placing the bolt carrier group on a flat surface, you should replace them.
It can be tempting to buy a parts kit in a ziplock bag and throw it in a desk drawer, but the point of keeping spare parts is to have replacements organized and accessible. If you often shoot or participate in formal matches, you should carry spare parts with you, either in your range bag or in a pouch designated for them.
If you’ve set aside space in your home or garage for working on your guns, you should consider buying a set of trays or drawers specifically for storing spare parts.
Tools and Accessories
A selection of spare parts should accompany a cleaning kit and other tools necessary for maintenance. Your rifle is a rugged piece of equipment, but it needs to be broken down periodically for cleaning, lubrication, and inspection.
Factors Affecting Wear
The AR-15 rifle is durable and should last for years, but how rapidly parts wear out depends on several factors, such as the caliber of your rifle, how well you clean and lubricate it, the type of ammunition you fire, your rifle’s gas system and buffer, etc.
One of the most important factors regarding the lifespan of a mil-spec rifle will be the round count. If you don’t fire your rifle often, you’re probably not as likely to experience a part break. However, spare parts are also a hedge against the possibility of loss or future shortages.
If you want to know more about the AR-15 parts the will most likely to fail, then check out this components guide here.
As part of being the owner of an AR-15 rifle, you should consider keeping spare parts in reserve. You never know when a part will break or when you’ll lose one—don’t wait until the last minute to build a supply.