The discussion begins with a basic explanation of the AR-15 buffer system in a direct-impingement rifle. The buffer and spring assembly, retained by a small pin in the buffer tube, slow the bolt carrier as it travels rearward and then drive it forward again to strip a new round from the magazine and chamber it. Without a functioning buffer system, the rifle would fire only once and fail to cycle properly. Several buffer types and weights are outlined: a standard carbine buffer at about 3 ounces, an H buffer at 3.8 ounces, an H2 at 4.6 ounces, an H3 at 5.1 ounces, and an H4 at about 6.8 ounces. Heavier pistol-caliber and AR9-style buffers can exceed 8 ounces because direct blowback systems rely solely on cartridge pressure to move the bolt, often producing sharper felt recoil that benefits from more buffer mass. A longer rifle buffer, around 5 ounces, is also mentioned, typically used with fixed stocks and longer buffer tubes.
Testing shifts to a 16-inch direct-impingement rifle fired unsuppressed while swapping through the different buffer weights. Five rounds are fired with each buffer to observe ejection pattern, felt recoil, and basic reliability. With the 3-ounce carbine buffer, the ejection pattern appears to land in a generally acceptable area, and the rifle cycles normally. Moving to the 3.8-ounce H buffer and then the 4.6-ounce H2 buffer, changes in recoil are subtle and difficult to distinguish shot to shot. The shooter notes that any differences may be more obvious when jumping directly from the lightest carbine buffer to the heaviest H4, assuming the rifle still cycles. With the 5.1-ounce H3 and then the 6.8-ounce H4, the rifle continues to function, and there is a slight impression of reduced muzzle rise with the heavier buffers. However, the test is limited to a clean rifle and a short firing sequence, so long-term reliability with heavy buffers in a fouled system is left as an open question.
The same 16-inch rifle is then fired with a SureFire SOCOM 556 RC2 suppressor installed, again using each buffer weight in turn. With the 3-ounce carbine buffer, the rifle is clearly overgassed, throwing brass forward toward roughly the 2 o’clock position, although gas to the shooter’s face remains manageable. The H buffer at 3.8 ounces still shows an overgassed ejection pattern, but recoil remains comfortable despite the added weight of the suppressor. With the 4.6-ounce H2 buffer, ejection begins to move slightly rearward but is still more forward than ideal for a suppressed setup. The 5.1-ounce H3 buffer brings the ejection pattern closer to the 3 o’clock area, which is considered more desirable. Finally, the 6.8-ounce H4 buffer produces what is described as near-ideal performance with this gas system length and suppressor combination, placing brass between about 3 and 4 o’clock and providing smooth, controllable recoil. The segment emphasizes that forward ejection suggests an overgassed system, while ejection far to the rear can indicate undergassing or potential short-stroking.
Attention then turns to a 10.3-inch Mark 18-style carbine with a carbine-length gas system, fired unsuppressed while changing buffer weights. With the 3-ounce carbine buffer installed, the ejection pattern appears more forward, indicating an overgassed condition typical of short 5.56 barrels. Swapping to the 3.8-ounce H buffer brings the ejection slightly rearward, and the rifle still has noticeable but expected recoil for a compact 5.56 platform. The gun carries additional accessories that add weight, which helps moderate movement. Moving to the 4.6-ounce H2 buffer, the ejection pattern settles into the preferred zone, roughly around 3 o’clock, and recoil remains manageable. With the 5.1-ounce H3 buffer, extraction still looks consistent and on target, suggesting the system tolerates the heavier buffer without reliability issues in this clean state. Installing the 6.8-ounce H4 buffer also results in good function and a favorable ejection pattern, leading to the observation that such a heavy buffer might be beneficial, though there is concern that once the rifle becomes dirty and carbon fouling increases, the added resistance could eventually compromise reliability.
The Mark 18 is then tested with the SureFire SOCOM 556 RC2 suppressor attached, starting again with the 3-ounce carbine buffer. With the suppressor installed, the short barrel and carbine gas system show clear signs of being overgassed, with brass thrown at a sharper angle and more forward than desired. Switching to the 3.8-ounce H buffer produces slightly improved recoil characteristics, and the difference compared to the carbine buffer becomes more noticeable under suppression. Ejection remains forward of the ideal zone, reinforcing that the system is still overgassed. The segment suggests that heavier buffers such as the H2, H3, or even H4 may be more appropriate for a suppressed 10.3-inch setup, but detailed results for each heavier buffer under suppression are not fully explored in this portion of the test. The broader takeaway is that short, suppressed 5.56 carbines often benefit from increased buffer weight to bring ejection closer to the 3 to 4 o’clock area and to moderate the added gas and recoil impulse introduced by the suppressor.
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