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Paul Cat

SAK moderator, loud first shot.

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Evening all.


I've a SAK moderator on a CZ 452 using (depending upon which box I grab in the dark) either Eley Subs or Remington. At first I thought I was imagining things or it was coincidence that my first shot of the day was toward a hard backstop but I'm now convinced that the first shot always creates a loud crack, almost as loud as my HMR. Each shot thereafter is as quiet as you would expect.


Any ideas?

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1 - is it a new mod ?  sometimes they need to "bed in".  2 - I sometimes find Remington, and particularly CCI - which I've stopped using are "cracky".  The new Eley subs are consistently quiet

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it is known as first round pop (FRP).

It is the oxygen burning up inside the moderator on the first shot, following the first shot the moderator chambers are full of carbon dioxide as a result of the burnt gasses, but that additional oxygen present on the first round makes it a more energetic explosion and it can be heard louder.

I'm hesitant to post this link as some of the content was contraversial (Using blanks with a moderator as a means of testing efficiency of slowing gasses) however it explains the phenomenon in greater detail - http://blog.stegough.com/moderators-suppressors-first-round-pop/

Hope this helps.

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It's far from new! Looks as if it's been around the block a few times to be honest. I wondered if a baffle had perhaps come loose but had yet to check that.


Then came TattooedGun's reply. Turns out it's a real thing. Thanks TG.

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Ive got the same mod, Ive never noticed on mine. Going to listen out now next time to see if I can hear it as well. Never heard of FRP before.

Thanksfor the info.

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