The AR-15 platform guns are among the most popular of today's modern sporting rifles.
One of the key components of the rifle is the buffer with its tube and spring, which, as a unit, serve a dual purpose.
Let’s have a look at the function of buffers and how they can be an upgrade to improve your AR-15 experience.
At a Glance: Our Top Picks for AR-15 Buffers
- OUR TOP PICK: JP Enterprises Silent Captured Spring AR-15 Buffer System (GEN 2)
- RUNNER-UP: Bravo Company AR-15 Buffer Tube Assembly Kit (Mil-Spec)
- BEST BUDGET OPTION: Spike's Tactical AR-15 Buffer Tube Assembly Kit (Mil-Spec)
Comparison of the Best AR-15 Buffer Kits and Spring Systems
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How to Choose an AR-15 Buffer
When choosing a buffer for your AR-15, you should focus on the following key aspects to ensure you get the most value for your money.
Tungsten or Steel Material
While you can find buffers made of aluminum, that material is lighter than either tungsten or steel and won’t work with as many stocks. Tungsten and steel are both dense and durable enough to withstand frequent AR-15 use, so they’re preferred amongst most AR-15 enthusiasts.
Spring Quality
The spring included in your buffer can affect the overall functionality of your rifle. Springs come in variable lengths, even though they all have about the same diameter. Try to match a carbine spring at about 10.5 inches and a rifle spring at about 12.75 inches. You should also try to find a spring that has a smooth surface or a special lubricated finish to improve operation.
Buffer Length
Similar to spring length, the length of your buffer matters a great deal. You cannot interchange rifle and carbine buffers with each other. Rifle buffers are typically longer and they fill the extra space of the typical AR-15 rifle tube. Carbine lengths are better if you are making a build with a collapsible stock. You can also find plenty of mil-spec carbine buffer tubes, so these should be fairly common, no matter which market you try.
Function of the AR-15 Buffer
The buffer tube forms a protrusion along the lower receiver and serves a dual function. It encapsulates the buffer with buffer spring (also called the action spring). It works as the attachment point for the buttstock, but also for the recoil buffer in the buffer assembly is the contact point for the bolt carrier to move rearward. That makes it a crucial element for the AR’s cyclic action.
After firing, the bolt carrier moves back into the buffer and the action spring recoils. It then pushes the buffer and bolt carrier forward, thus loading the next cartridge and closing the bolt for the next shot.
Typically, a factory AR-15 will normally be a bit over-gassed by the manufacturer to ensure reliable function with various types of ammunition and operating conditions. However, if you are building your own rifle, you can tune how the rifle cycles in two ways. One is adjusting the gas management using an adjustable gas block or by adjusting the weight of the reciprocating mass - the buffer. The buffer and spring are the only two mechanical parts that affect the rifle’s cycling and can noticeably reduce the felt recoil.
For AR enthusiasts, it’s important to remember that rifle barrel length and weight directly relate to the buffer weight. In short, the lighter the barrel you have, the lighter the buffer you need to use. AR-15 buffers are available in a variety of weights and markings with heavier buffers for pistol-caliber carbines through rifle buffer models. They can weigh from about three ounces to around five ounces.
Review of the Best Buffer Kits and Spring Systems for the AR-15
We’ve explored a lot of buffers and now present you with some suggestions to avoid the hassles of scouring the internet and to optimize the gas delivery on your custom rifle.
Best Overall:
JP Enterprises Silent Captured Spring AR-15 Buffer System (GEN 2)
Pros
Cons
What Recent Buyers Report
Recent users of this buffer spring report that the lightness of the spring shaves off a lot of recoil and stress from their build. Controlling their rifle with the spring installed was easier than before and installing the buffer spring in the first place was easy, as well.
Why it Stands Out to Us
We think that a suitably light buffer spring is a necessity for anyone putting together a mobile AR build. Its superior weight distribution and consistent performance make it a strong contender for rifles that aim to have as little extra mass as possible.
Since the standard-diameter spring rubs the internal surface of the buffer tube, the Black Rifle is known to have a "twang" sound after firing a cartridge. This can be especially pronounced during shooting with a suppressor. If you want to avoid this “twang” effect, the solution is to use a JP Enterprises Silent Captured Spring AR-15 Buffer System.
In this system, the buffer spring that does not contact the inside walls of the tube. The Gen 2 drop-in, captured-spring recoil system boasts an aluminum guide rod to reduce the unit’s overall weight. It also has highly-polished stainless steel parts, guaranteeing smooth and precise operation. It’s paired with a hard polymer nylon spacer that measures 1-5/8 inches.
The SCS smooths out the actual operation of the gun and minimizes bolt bounce. This results in sound reduction. The JP system seats the bolt much better and more consistently on the round, eliminating the friction of standard buffer components.
This unit can be modified by changing out the spring or replacing the steel weights with tungsten for a heavier buffer. Combining the heavier buffer weight, spring tension, and an adjustable gas block will help reduce the noise to a minimal amount. It will also help reduce the amount of pressure in the upper receiver.
More importantly, the SCS is a self-contained unit that can be used in carbine or rifle-length receiver extensions. It can also be used with short-barreled rifles (SBRs), suppressed weapons, select-fire ARs, and piston-operated ARs.
However, this system is not compatible with 9 mm AR variants or any blowback system using a solid carrier.
Who Will Use This Most
AR enthusiasts who don’t like having to use rifles or carbines with a lot of recoil will enjoy the gentleness that this spring brings to the table. It’s particularly suitable for shooters who struggle with keeping their rifle in check at the range, although you’ll need to make sure the spring fits with your current build channel before buying.
Bottom Line
If the spring fits your current build frame, feel free to pick this up and see the results for yourself. You won’t be disappointed with the performance improvements it can provide, and you’ll notice how much lighter your AR feels right after you finish its easy installation.
Runner-up:
Bravo Company AR-15 Buffer Tube Assembly Kit (Mil-Spec)
Pros
Cons
What Recent Buyers Report
Those who've used this buffer kit most recently report that it is a high-quality purchase, with the included spring, buffer, and castle nut all being of high-quality and exceptional durability. However, the asking price is a little too high, given that it doesn’t come with a sling mount. Instead, you’re forced to stick with a standard plate for your build.
Why it Stands Out to Us
We think the overall durability of each piece makes this a worthwhile buy. The anodized finish is particularly nice for reducing corrosive damage and the castle nut is also heat-treated for extra strength and given its own phosphate finish. This improves durability. Even the high-tensile steel spring is super-strong, although it’s a little heavier than we would’ve liked.
Another buffer assembly kit comes from a company with a well-deserved reputation for excellence. These are extremely popular among law enforcement officers, military personnel, and shooting sports competitors. Bravo Company’s complete buffer kit consists of a mil-spec receiver extension (buffer tube), receiver end plate, M4 castle nut, carbine-action spring, and carbine standard buffer assembly.
The six-position buffer tube is built to mil-spec dimensions from impact-extruded 7075-T6 aluminum. Also included is a standard 3 oz. (85g) carbine buffer, a carbine action spring, and a castle nut made of high-tensile steel for improved strength and durability.
There are a few issues with the finish not being perfect. Also, some buyers might hope for a sling mount rather than a standard plate, considering the brand and price range.
Who Will Use This Most
Heavy-duty AR builds will be able to benefit from each of these pieces more than others. Anyone who is looking to spend top-dollar for high-quality materials will love what comes in this kit. It might be a little expensive upfront, but it’s well worth the cost when you won’t have to replace the kit in a few months.
Bottom Line
Overall, the high asking price is worthwhile when you consider how long each of the individual pieces will last, even under heavy use. Even though it doesn’t come with a sling mount, you should still be able to use it for most heavier-duty AR builds and the fact that it comes with mil-spec designs means you can use it with most stock varieties.
Best for the Money:
Spike's Tactical AR-15 Buffer Tube Assembly Kit (Mil-Spec)
Pros
Cons
What Recent Buyers Report
Those who’ve used this recoil buffer recently report that it does an effective job at reducing the recoil and vibration you’ll experience when firing your carbine. Most report that it does an excellent job at reducing rifle shaking and reducing the overall volume of the weapon, as well.
Why it Stands Out to Us
Any recoil buffer that gives the choice of weight to the user earns extra points in our book. This is a great choice if you already know the ideal weight arrangement for your build, and no matter which you choose, the recoil buffer will reduce your felt recoil and help make your next session at the shooting range more comfortable and enjoyable.
The Spike's AR-15 buffer tube is machined of durable 7075-T6 aluminum with a Type III hard-anodized coating. The buffer springs are made of electro-polished 17-7 stainless steel designed to resist the binding that can occur with lower-quality springs. While these mil-spec springs are very popular, the real favorite among gun aficionados is that this model is weighted with tungsten powder.
The aluminum body measures 3¼" (8.2cm) long and is topped with a polyurethane bumper. The kit comes in three weights, all with tungsten powder to absorb the recoil efficiently and quietly. You can either select the standard-weight ST-T1 (3 oz.) buffer (LDTP) filled with low-density tungsten powder. The ST-T2 filled with high-density tungsten powder (HDTP) for extra weight (4.1 oz.). Finally, you can use ST-T3 filled with an ultra-dense tungsten bar that weighs 5.4 ounces, giving you maximum recoil control in full-auto mode and on suppressed weapons.
This unit is a purposefully assembled buffer kit that gives the best combination of recoil control and reliability in your carbine with an M4-type adjustable stock.
With this AR manufacturer, which creates high-quality parts, you can’t go wrong. The only negative would be that’s it only wrapped in a plastic bag without paper or bubble wrap to protect it in transport.
Who Will Use This Most
Anyone who has an AR build with a little too much recoil will benefit greatly from any of the three buffer choices. Since they’re all made with fantastic materials and all do a great job at lowering volume and rifle shaking, it’s almost impossible to go wrong with any of the choices.
Bottom Line
This is a phenomenal pick if you’re in the market for a variable buffer with a few different weight choices. You can also get a few of this same buffer and switch them out if you like to subtly alter the performance of your AR build from time to time.
4. Rock River Arms - CAR-15/M4 9 mm Carbine Buffer
Pros
Cons
What Recent Buyers Report
Recent users of this carbine buffer mostly have good things to report. It’s easy to install and does a great job of stabilizing the motion of any AR carbine build. It’s simple steel aesthetic and black oxide finish allow it to work with most AR builds in terms of looks, as well.
Why It Stands Out to Us
We found this buffer to be a good choice for fitting to most standard carbine builds, even though it lacks some extra pieces you would find in a full-on buffer kit. Even though it’s a little heavy, it shouldn’t negatively affect most AR shooting, so long as you install it correctly. It isn’t mil-spec, so keep this in mind when thinking about combining with certain stocks.
This Rock River Arms 9 mm buffer is an essential piece if you want to convert your AR-15 to shoot 9 mm bullets and reduce the cycle rate and felt recoil of the AR-15. The RRA carbine buffer weighs approximately 5.6 oz with a traditional length of 3.300″, like standard Colt 9 mm buffers. It features steel construction, a polyurethane bumper, and a phosphate finish.
There are several side benefits to the Heavy Buffers 9 mm Q Buffer. It offers a smoother function, less felt recoil, and a reduced rate of fire. It uses the same buffer spring as the .223/5.56 and is heavy enough to keep blowback gases to a minimum.
The Rock River 9 mm AR-15 Buffer is a self-contained unit held together with very rugged roll pins.
Some shooters hold that a 9 mm buffer needs to be at least 3.6 inches long to prevent the bolt catch from breaking, so this unit comes up short there.
Who Will Use This Most
We think commercial stock carbine users will really benefit from all that this buffer has to offer. Because it’s easy to install, it’s a great starter buffer if you’re teaching someone or yourself how to put together AR builds for the first time, as well. Since it’s simple and has a robust oxide finish to reduce corrosive damage, there’s a high likelihood it’ll last for a long time, as well.
Bottom Line
Overall, it’s a decent carbine buffer with a reasonable price tag, given its oxide finish. We still wish it would work with mil-spec stocks and came with its own spring, but since it works with most spring weights and varieties, it’s still a worthy option.
5. Bushmaster Firearms Int. LLC AR-15/M16 Rifle Buffer
Pros
Cons
What Recent Buyers Report
Recent users report that while this is a great buffer for select AR rifle builds, it only accepts certain sizes of springs so you should make sure your current springs are compatible before finalizing a purchase. Otherwise, it’s an affordable rifle buffer that's easy to install and which is made from durable machined steel.
Why it Stands Out to Us
We think this is a great budget option for many of the more expensive AR rifle builds. Since the rest of your rifle will likely cost a pretty penny, getting a functional but affordable rifle buffer is a great way to cut down costs. Even with its affordable price, this is still a durable buffer that is perfectly sized for the majority of typical rifle builds.
This rifle buffer system from Bushmaster Firearms works with rifle receiver extensions (in other words, it will fit rifle-length buffer tubes). It weighs 5.4 ounces, the equivalent of an H3.
This steel construction has five steel weights and one spacer inside. It’s topped with polyurethane bumper.
This simple rifle buffer is typically available in only one weight (around 5 oz.) and cannot be modified or adapted to different types of load or suppressors.
Who Will Use This Most
We think AR rifle enthusiasts who make a lot of standard rifle builds will appreciate the consistency that this buffer brings to the table. Since it’s easy to install, this is also a great choice for beginner AR builders who are just starting to learn the ropes.
Bottom Line
So long as you can handle the higher weight, this is a great pick for your first rifle buffer or if you need something affordable. While it lacks a special finish to prevent damage over time, the low cost offsets this risk somewhat.
6. FM Products - AR-15 FM-9 Heavy Buffer
Pros
Cons
What Recent Buyers Report
Recent users of this buffer have nothing but good things to say. Although it’s a little heavy, it works great when combined with pistol caliber carbine builds and the extended length allows for proper functioning in longer AR builds. Since you don’t have to include a spacer, it’s easy to mesh with most AR builds right out of the box.
Why it Stands Out to Us
Having a buffer that you can switch between pistol or AR builds can be a nice change of pace, particularly if you’re a hobbyist gunsmith and like to mess with your builds from time to time. The nitride finish helps with the easy install by improving lubrication and enhancing its wear resistance, so it lasts longer even under heavy use.
This heavy buffer is fully compatible with any blowback 9 mm upper receiver for true versatility on any number of your weapons, ensuring you can standardize your buffers throughout your arsenal. Finished with a special nitride melonite salt bath and QPQ, the heavy buffer is unique in offering lubricity and excellent wear-resistance for a long time to come, no matter how often or heavily you use your AR-15.
At 6.4 ounces in weight, the FM Products heavy buffer provides a heavy-duty performance you can feel. Although it may take some getting used to, it will greatly improve recoil over stock buffers and is immediately noticeable upon upgrade. The extended length requires no spacer, which also helps to prevent bolt catch breakage. After equipped, you’ll notice it reduces the rate of fire for better control and less cumulative recoil.
Seasoned gun owners who’ve replaced buffers in the past may be wondering if there are sliding weights for anti-bounce or dampening inside the buffer, and there are not. However, this buffer works very well as-is.
All FM Product offerings are domestically produced in the United States from high-quality materials and the AR-15 FM-9 Heavy Buffer is no exception. It is a solid buffer that will last a long time.
Who Will Use This Most
As we implied, anyone who likes to take apart and put their guns back together will find a lot of use with this buffer. Its versatility is its main strength, but it’s also just well put together. The 4340 steel is an excellent material that is sure to last a long time.
Bottom Line
This pistol buffer can be integrated with most AR builds, provided you have the expertise to do so. Alternatively, you can always take this to a licensed gunsmith and get the most bang for your buck. Its extended size allows it to work with most AR builds, despite its original function.
A heavier buffer may take a little getting used to for new gun owners, but the improved cycling and drastically reduced recoil make for a much better experience. While we’d prefer a warranty on this heavy buffer, the quality materials and superior U.S.A. craftsmanship make it a top choice.
Types of Buffers
Buffers may be made of lead or aluminum, but the most frequently used materials today are steel and tungsten because these materials are both heavy and dense. While steel weighs around 0.28 lb. per cubic inch (PCI), on average, a tungsten buffer commonly weighs about 0.70 pounds PCI, on average.
There are four basic configurations of AR buffers. Within these, there are also a variety of buffer weights and designs available on the aftermarket. Here are some averages, but of course there are variances among manufacturers.
- The standard .223/5.56 mm semi-auto only carbine buffer is usually unmarked. It consists of three steel weights and usually totals about 3.0 oz. in weight.
- The most common buffer, marked “H” for heavy, features a combination of one tungsten and two steel weights and commonly weighs around 3.8 oz.
- H2 buffers feature the same design as the H buffer. This version is better with heavy barrels since it weighs around 4.7 ounces, on average. It is comprised of two tungsten and two steel weights inside the buffer.
- H3 is similar to the H and H2 but it was designed to work with longer and heavier barrels. The H3 buffer includes three tungsten weights and often weighs about 5.6 oz.
Besides the weight, there are two different sizes of buffers - rifle-length and carbine-length.
Mil-spec vs. Commercial Buffer Tubes
Another significant difference is the diameter of the area where the stock slides onto the tube. With the original mil-spec buffer tube, the threads at the front are actually a larger diameter than the rest of the tube. Mil-spec tubes are a forged, one-piece design with an outside diameter measuring 1.148".
The threads on mil-spec buffer tube are rolled on. On the other hand, commercial-spec buffer tube threads are cut into the front end with a lathe, just like any other threaded pipe. This allows for a lower manufacturing cost. Since the commercial receiver extension tube is a touch larger in diameter, measuring 1.168", mil-spec and commercial versions are not compatible with each other. So stocks that fit one will not fit the other.
There are no functional differences between the two. But the prevailing opinion is in favor of mil-spec buffer tubes for the simple reason that more stocks are available.
Knowing When It’s Time to Change Your Spring
Since the buffer assembly is a mechanical part, it is necessary to periodically evaluate buffer spring lengths to ensure your AR-15 will continue to perform consistently. Standard carbine springs measure 10.5” and usually have between 37 and 39 coils. Rifle-length springs measure 12.75” and boast 41 to 43 coils on average.
This spring usually is made of steel alloy and use a spring tension weight that is 10% over the standard spring. The spring shortens over an extended period. When you notice the carbine spring is less than ten inches long or the rifle spring is less than 12 inches long, you will need to replace them.
Rifle and carbine springs are NOT interchangeable. You should never consider exchanging rifle and carbine buffers.
How to Install an AR-15 Buffer Kit:
Replacing the factory buffer on your AR-15 can greatly enhance your weapon’s recoil. If you’re ready to reap the advantages, follow our steps below, and reference our video for visuals:
- Ensure you have all the tools needed: You will need a castle nut wrench and your buffer kit. Your buffer kit should have a buffer tube, takedown pin, buffer retainer, end plate, castle nut, buffer retainer spring, takedown pin detent, and takedown detent spring.
- Thread your castle nut onto the buffer tube, being sure that it ends securely in place.
- Place your receiver end plate over the buffer tube. Be sure the bump on the end plate faces the receiver. This engages the cavity on the black of your receiver. Screw the buffer tube into the receiver a few threads, helping hold it in place.
- Insert retainer and the buffer retainer spring into the lower receiver.
- Push the retainer down and thread the buffer tube. It should hold the edge of the detent, allowing the tip to protrude.
- Insert the takedown pin, the takedown pin detent, and the spring.
- Now slide the end plate to the receiver. Be careful of the takedown pin detent spring.
- Tighten the castle nut to the receiver with your finger. Rotate the takedown pin until your detent falls into position.
- Tighten with your wrench, and you’re done! Enjoy improved recoil on your AR-15!
Conclusion
By altering the weight of the buffer, you can modify the performance of how your rifle cycles. Finding the right buffer assembly and buffer weight will guarantee you'll be able to reduce felt recoil and recover more quickly between shots. Ultimately, you’ll be able to enjoy a better experience every time you use your AR-15.
