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What is First Round Pop?

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What is First Round Pop?
« on: March 24, 2016, 10:51:24 AM »


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I found this very interesting and wanted to share it. Hope you enjoy it.

Most people who start looking at suppressors, come across the term First Round Pop (also known as FRP) pretty quickly.

At a very basic level, the term First Round Pop is referring to the first round thatís fired through a suppressor after itís been out of use.  Since the suppressor is initially filled with oxygen, there will be an additional Ďpopí as the oxygen burns out Ė which makes the first shot louder than subsequent shots.


Depending on the suppressor, firearm, ammunition, and environment; the FRP can range from almost non-existent to very noticeable.  Unfortunately, because of all the variables involved, itís extremely hard to get consistent FRP measurements.

Keep in mind that, although FRP can be noticeable, the suppressed shot will be just slightly louder than subsequent rounds Ė so itís not something to be overly concerned about when it comes to either overall enjoyment or hearing safety.

Having said that, there are several factors that tend to impact FRP fairly consistently:

Although FRP is definitely present on higher pressure calibers, itís not as noticeable because the rounds are so much louder.

As a result, youíll hear a lot of talk about it when referring to rimfire or pistol suppressors Ė but nobody really cares on a suppressed .338 Lapua. :)
Monocore Suppressors

Some suppressors are designed with a core that comes out as a single piece: like the SilencerCo Sparrow SS.  Those single-piece designs are typically referred to as Monocore Suppressors.

As a general rule, a monocore suppressor will have a louder FRP than a suppressor that uses individually stacked baffles.  Some examples of individual baffle designs include the Tactial Solutions Axiom or the Griffin Revolution 9.
Bore Size

Itís very common to use a larger bore suppressor for use with multiple calibers.

For example: a .45 pistol suppressor works great for suppressing a 9mm or .40 handgun; or, a 7.62mm suppressor will come very close to the performance of a 5.56mm suppressor.

Unfortunately, there are always trade-offs Ė and one of them is youíll generally have a noticeably louder first round pop when shooting sub-calibers through a larger bore suppressor.
Time Since the Last Shot

After hearing about FRP, one of the first questions we get asked is how long a suppressor can sit unused before FRP will occur again?

This is hard to answer because itís extremely dependent on the environment.  For example, on a windy day at the range youíll get that First Round Pop more often than you would shooting at an indoor range.
Working Around FRP

In most cases, First Round Pop probably isnít enough of an issue to worry about; since, aside from just sounding louder, it doesnít cause any issues.

Having said that, if itís bugging you and you want to reduce it as much as possible, try adding just a teaspoon of water to the rear of your rimfire or pistol suppressor before shooting.

I would NOT, however, recommend adding water to a rifle suppressor in most cases.

At the end of the day, First Round Pop can definitely be noticeable on low-pressure calibers (like pistol & rimfire); but, itís not that big of a deal for most users.

Personally, Iíd suggest using FRP as a tie-breaker if you have 2 suppressors youíre interested in; but, I probably wouldnít consider it as a primary requirement in most casesÖ
SBR's, AI's and Suppressors. The only way to fly.