Buffers and Springs Explained

Now that we’ve covered the function and varieties of buffer tubes, we can drill down to the innards of the tube and focus on the buffer and buffer spring. To begin, the buffer and buffer spring are housed within the buffer tube, and are crucial elements for the AR’s cyclic action. The buffer is the contact point for the bolt carrier to move rearward within the buffer tube and the spring resides in the most aft position of the assembly. When the buffer spring recoils, it pushes the buffer and bolt carrier forward, thus loading the next round of ammunition and closing the bolt for the next shot. While all dire AR rifles function similarly with this system, there are mainly two different sizes of buffers (rifle length and carbine length). The important headline here is that these two sizes are NOT interchangeable.

Rifle vs Carbine

Rifle length buffer weights are used when a standard A2 buffer tube is installed for a fixed stock. The extra length helps to fill the void in the longer A2 rifle buffer tube. Carbine buffer weights are used with most collapsible stocks that utilize a carbine buffer tube. Generally, fixed stocks use an A2 smooth buffer tube and adjustable stocks use a carbine buffer tube. Most of the stocks on the market use a Mil-Spec carbine buffer tube and are adjustable for length of pull. 

Tuning

While the buffer and buffer spring are commonly used to “tune” a rifle, the rifle builder must recognize that the buffer and spring are only two mechanical components that affect the cyclic action. Ultimately, other factors including barrel length, gas port size, gas tube length, dwell time, use of suppressor, etc…all affect the gas management. Most off the shelf ARs are typically “over gassed” from the manufacturer to ensure reliability with various types of ammunition and operating conditions. When building a custom rifle, the variety of buffers and springs available allow the rifle builder options to optimize the gas delivery.  These are not the only options by the way. We will be covering how to tune your action and gas system in a future article. 

Buffer Type Overview

Below are the different weights of carbine buffers available. These are average, as there are variances from manufacturer to manufacturer.

• Carbine – 3 oz. – 3 steel weights inside buffer
• Heavy (H) – 3.8oz. – 1 tungsten weight + 2 steel weights inside buffer
• H2 – 4.7oz. – 2 tungsten + 2 steel weights inside buffer
• H3 – 5.0oz – 3 tungsten weights inside buffer
• HSS - 6.5oz
• XH - 8.5oz
• Rifle Length – 5.0oz. – 5 steel weights + 1 steel spacer inside buffer
• There are also heavier buffers for pistol caliber carbines, but we'll leave that subject for another post in the near future. 
• Some manufacturers use “steel shot” inside their buffers to equate their buffer weights to the standard steel/tungsten specs above. While there is argument amongst some builders that the movement of the steel shot inside the buffer affects cycling, there are no real case studies known that show any pros/cons for the buffers that are made with the steel shot.

Illustration-cutaway of a standard buffer

Buffer Spring Overview

For the most part, buffer springs are all fairly similar. Both rifle and carbine springs have the same diameter, just different lengths. While it’s more common to “tune” a rifle by changing the buffer, different spring rates are another place where the rifle builder has choices. Most aftermarket springs use a spring tension weight that is +10% over the standard spring and they will be labeled as such. 

• Standard Carbine Spring – Measures 10.5” with 37 to 39 coils
• Standard Rifle Spring – Measures 12.75” with 41 to 42 coils

Because standard diameter springs rub the internal surface of the buffer tube, the AR platform is known to have a “twang” sound after firing each round. Some buffer tube manufacturers (such as V Seven Weapons, LMT and VLTOR) have developed finishes or precision grind the inside of the buffer tube that helps to reduce this by increasing lubricity and/or smoothness of the surface. The only way to eliminate this “twang” effect is to use a buffer spring that does not contact the inside walls of the buffer tube (more on this in a moment…). JP's Centerless-Ground and polished springs are a cost effective way to decrease the buffer noise and smooth out the buffer spring action. The Wolff XP buffer springs are also a great option for smoothing out the recoil system by adding a little bit more tension. 

Butter Smooth & No More Twang…

For a really smooth, quiet action, JP Enterprises has gone against the grain and developed a unique solution. 

This combination buffer-spring assembly eliminates the friction of standard buffer components, resulting in outstanding smoothness and sound abatement, as the spring does not rub the inside of the buffer tube. The spring is removable from the assembly for custom tuning and cleaning. For tuning to a certain load, you can replace the steel weights with tungsten for a heavier buffer, as well as change out the spring with the JP Spring Kit. Both the AR-15 and AR-10 versions of the JP Silent Captured Springs are functional in rifle and carbine length buffer tubes by either using or omitting the included insert. The AR-15 version fits and functions in any AR-15 variant, regardless of caliber and the AR-10 version should fit and function in any large-frame AR-10-type platform. The JP system also does not require the buffer retainer to be installed, thus simplifying the initial assembly process, as well as maintenance of the rifle. Another option is to shave the tip of the buffer retainer until it becomes flush with the inner part of the buffer tube. 

If shooting with a suppressor is in your future, the silent captured springs deadens the sound of the buffer system cycling to reduce the noise to a minimal amount. The added benefit of tune-ability is a plus for use with a suppressor so you can select exactly how you want it to function. The heavier buffer weight and spring tension will help keep the bolt locked as long as possible, letting more gas leave the barrel before unlocking. This will help reduce the amount of pressure in the upper receiver, as well as reduce the amount of gas face you'll experience while shooting a suppressed direct impingement rifle. JP offers the "Heavy" version of their captured springs, which comes with the tungsten weights direct from JP. When using a suppressor or a particularly hot caliber, we do recommend the heavy version or tune your own system by using the standard spring with the optional weights and springs until it's perfect. An adjustable gas block helps take some of this time spent tuning away, but increasing the dwell time with a heavier buffer is always a good thing in this instance. The longer the bolt stays locked, the longer the blast has to flow down the rifle before blowing back out of the chamber, decreasing the amount of pressure and carbon in the upper receiver. A longer dwell time also helps with keeping gas and oil away from your face...for the most part anyway. 

Choices, choices, choices…

So, which buffer is right for me? If you get a buffer/spring combination that is too heavy the rifle won’t be able to push the spring back and pick up a fresh round. If you get a buffer/spring combination that is too light, the bolt carrier might move too fast and out run the next round coming up from the mag. Any combination that is too light can cause damage to your buffer tube and cycling system. 

For a general purpose 5.56 build, H buffers are a great starting point and consistently run reliably. When building a rifle in any caliber, it becomes a test of trial and error to get the weapon to function as desired with your choice of ammunition. 

We (Strong-Side Tactical) highly recommend the JP captured spring system, as it provides a superbly smooth cycling action and is tunable. However, we do understand that the price shies many people away. While we consider the Silent Captured spring the best buffer/spring on the market, the other combination that we recommend is an H buffer and JP polished buffer spring.