What is first round pop?
When using a suppressor, the first shot may be louder than subsequent ones due to “first round pop.” Available oxygen in the suppressor may combust, resulting in an above average report from the suppressed weapon. Generally speaking, most all suppressors have first round pop to different extents. Some are not detectable to the human ear while others are extremely noticeable, primarily on rimfire silencers. Suppressor design, ammunition type, atmospheric conditions, and the host firearm are all factors in determining the extent of a suppressor’s first round pop.
The largest determining factor in first round pop is the design of the suppressor. As a very general statement, monocore baffles are more prone to poor first round performance. If you were to compare two monocore rimfire suppressors, one could have significant first round pop, and the other could demonstrate virtually none. To complicate matters further, the host firearm will play a very significant role in first round pop. One specific suppressor may have noticeable first round pop on pistol hosts and virtually none on a rifle. If a significant amount of powder is burned before the projectile reaches the muzzle, as is the case with a longer barrel, it greatly reduces the amount of first round pop. Because of this, pistols and SBRs may allow first round pop to present itself on a suppressor that has not demonstrated any on a rifle.
The last large factor in first round pop is the environment. Environmental conditions, such as extremely high humidity, may reduce first round pop. A suppressor may exhibit very noticeable first round pop on a hot, dry afternoon. The same suppressor and host may not have any noticeable first round pop on an extraordinarily humid morning. High humidity, which results in water being introduced into the suppressors, leads us into our next topic.
Most pistol and rimfire suppressors can also be run “wet.” A very small amount of water or clear wire pulling gel can be put into the suppressor to greatly reduce first round pop. While this enhances how fast the gasses are cooled, it also increases pressure. It’s important to check with the manufacturer to insure running a particular suppressor wet is safe. A wet suppressor will demonstrate an increase in performance for the first few rounds, but it will return to normal fairly quickly.
Because first round pop is the more noticeable on rimfire suppressors than centerfire silencers, it becomes an important factor to many shooters when deciding which rimfire suppressor to purchase. Some examples of rimfire suppressors with virtually no first round pop include the Dead Air Mask, SilencerCo Spectre II, ThunderBeast 22 Take Down, and Rugged Oculus. With the basic understanding of what first round pop is and what causes it, the shooter can better determine if it’s an important factor in the purchasing decision.