Controlling Your Gas

At this point, we have discussed the way the gas system works and the importance of the right amount of pressure and flow through the gas system.

As we have discussed, the DI AR has an ideal range for gas flow and pressure. To make sure you have enough gas to run the system, you want to make sure the components are dimensionally appropriate and make effective use of as much gas harnessed at the gas port as possible. But you don’t want to dump too much gas through the system either. The question is, how do we control the amount of gas flowing through the gas system?

Too Gassy (easy to fix)

Too much gas is easy to deal with. There are several ways to control excess gas:

Deal with the excessive force generated by the gas with inertial mass (heavier buffer and carrier)
Deal with the excessive force generated by the gas with spring tension (buffer spring).
Deal with excess gas at the gas key (adjustable gas key; we will not discuss these further).
Deal with the excess gas at the gas block (adjustable gas block).

Most of these options are treating the symptoms of excess gas entering the system. The longer you wait to deal with the gas, the more ill effects it can have (and the more problems you create with the “solutions”).

Carrier Mass

We always recommend running full mass bolt carrier groups. A full mass carrier will always be the most reliable option. If your gun is over-gassed with a light carrier, swap it out for a full mass carrier; this could fix your issue.

In a standard caliber AR-15, light carriers are only good for one thing: finely tuned competition race guns that require every millisecond of advantage. These guns are always pristine, impeccably lubricated, and run consistently manufactured ammunition loaded into perfect magazines. However, when the ammo changes, the temperature changes, the gun gets dirty, or any other variable is introduced, guns with a light carrier are much more prone to malfunction. This is because their reciprocating mass (BCG and buffer) have lower inertia and are more sensitive to variation.

Buffer Mass

When your gun is over-gassed, the force generated by the gas system is more than the operating system needs to cycle. Inertia resists this force: a heavier reciprocating mass (BCG and/or buffer) will require more energy to get it moving.

Not every AR likes the same buffer weight. Unabated, each gas system length generates different levels of force to the BCG. You can manage these differences in force by swapping out your buffer to a different weight. The following table reflects the typical buffer weight that works well in each gas system length using a standard spring for the buffer system length (i.e. carbine spring for carbine receiver extension; rifle spring for rifle receiver extension).

If your gun is over-gassed (and showing symptoms of being significantly over-gassed), try switching to a heavier buffer. Experiment with different buffer weights and buffer spring combinations.

Buffer Spring Strength

The buffer spring absorbs, stores, and releases the energy transferred to the reciprocating mass by the gas system. A stronger spring will absorb and release more energy than a lighter spring.

Springs wear out. Your typical round wire buffer spring will wear out faster than you would think. As the spring wears out, it shortens and the tension applied to the reciprocating mass is reduced. This causes the mass to cycle harder and faster, which can result in malfunctions. As a rule of thumb, a typical round wire spring should be replaced once the uncompressed length shrinks below 10 1/16” (carbine) or 11 ¾” (rifle).

When you increase the inertia of the reciprocating mass (i.e. full mass carrier and heavy buffer), you should also consider the strength of the buffer spring. A heavier mass moving at the same speed carries more kinetic energy. The spring needs to be able to absorb this added energy, or it will simply slam into the back of the buffer tube.

Along with the buffer weight, playing with heavier spring weights can help you tune an over-gassed gun.

Sprinco makes a full line of buffer springs that can be used to tame any level of recoil. And the manufacturing process that Sprinco uses for all of their buffer springs results in a stronger, more durable, and longer-lasting spring.

David Tubb makes the best flat wire spring on the market. The properties of a flat wire spring offer higher bolt tension and a more linear (consistent) tension curve. They also last significantly longer than round wire springs.

Adjustable Gas Block

The best place to deal with excess gas is as close to the source as possible. This translates to an adjustable gas block. By restricting or bleeding off the gas pressure at the gas block, you can send just enough gas to through the gas system to cycle the gun. And if things change (change in ambient temperature, switching to lower/higher pressure ammo, worn parts, a dirty gun, under-lubrication, etc.), you can always dial the gas flow up or down.

There are generally two ways that adjustable gas blocks control the flow of gas: through restriction and through bleed off.

The restriction method effectively reduces the diameter of the orifice through which the gas flows to get into the gas tube. This restriction limits the volume of gas that can enter the system (as if you had a smaller gas port). This is how the most adjustable gas blocks work.

The bleed off style of gas block allows gas into the gas system (instead of preventing it), and then diverts excess gas out of the gas system.

Note that these two methods are not mutually exclusive in a gas block. Superlative Arms manufacturers adjustable gas blocks that can be set to operate in either restriction or bleed off modes.

Not Gassy Enough (hard to fix)

Dealing with too little gas is a lot harder. There are a couple of tactics that you can use.

Make sure that you are sending enough gas into the system (i.e. the gas port is the right size, make sure the gas port and gas block are aligned, etc.).
Keep the gas in the gas system by eliminating leaks in the system.
Reduce the inertia and spring tension.

Most gas ports are appropriately sized (or even on the big size), so you generally don’t have to worry about #1.

Unfortunately, most gas systems leak like a sieve and could use a bit of attention to tighten them up. The only way to address this is by focusing on dimensional tolerances of the various components of the gas system as you are building/re-building. We will explore tolerance in the next article.

In a standard caliber gun, if you are sending enough gas into the gas system and you are keeping it there, you should never need to play around with lighter BCGs, lighter buffers, and lighter springs. When you start playing around with lighter components, you will sacrifice reliability and durability. As such, we recommend option #3 as a last resort or for lighter loads (e.g. 300 AAC Blackout sub-sonic).

Get Social - Share This Page!

Tell Us What You Think!

Your feedback is really important to us. Our goal is to provide the highest quality content possible to help you on your AR journey. If anything isn’t clear, is missing, is incorrect, or otherwise needs our attention, we greatly appreciate you letting us know. It will help us continuously improve our content for the firearms community.