Clarification of Dry Fire #'s

[Billy Goat]

I tried searching some, and I haven't come up with an answer, but I might have missed it.


How is it being measured when a dry fire is recorded at over 120db?

I know its at shooters ear, but what exactly is that? 2" over the stock behind the action? 6 inches off?

Forgive my ignorance. Probably explained in depth somewhere.

 

[Ucsdryder]

I tried searching some, and I haven't come up with an answer, but I might have missed it.


How is it being measured when a dry fire is recorded at over 120db?

I know its at shooters ear, but what exactly is that? 2" over the stock behind the action? 6 inches off?

Forgive my ignorance. Probably explained in depth somewhere.

I saw this as well and just wrote it off as BS, but I’m glad you asked. Here are some example of things over 120db.

 

[Billy Goat]

I saw this as well and just wrote it off as BS, but I’m glad you asked. Here are some example of things over 120db. View attachment 1061714

I'm quickly going deaf, but I hadn't considered ear protection for dry fire practice.

 

[Q_Sertorius]

I tried searching some, and I haven't come up with an answer, but I might have missed it.


How is it being measured when a dry fire is recorded at over 120db?

I know its at shooters ear, but what exactly is that? 2" over the stock behind the action? 6 inches off?

Forgive my ignorance. Probably explained in depth somewhere.

I thought the “dry fire can register 121” was a way to illustrate that the meters just aren’t very good.

 

[Billy Goat]

I thought the “dry fire can register 121” was a way to illustrate that the meters just aren’t very good.

Maybe that's the case.

I haven't been following, but I seem to keep reading how something can't be 120db because that's quieter than the firing pin?

 

[Billy Goat]

Here's one of the things that came up from searching, maybe I wasn't understanding the context of it. But I don't see any mention of it being false, its saying that is dry fire numbers.

Am I out of context?



@Formidilosus

 

[Q_Sertorius]

Maybe that's the case.

I haven't been following, but I seem to keep reading how something can't be 120db because that's quieter than the firing pin?

In context, some people were reporting numbers that were highly unlikely. To make a point, Form showed that a meter could register that loud from just the firing pin dropping. And the rifle in question was clearly much, much louder than that.

From what I have read and heard, the meters, even very good ones, start to get really janky below 130 decibels. So, unless you know it was recorded in a proper setup with the best equipment, be skeptical of readings below that point.

When measured on a proper meter with a good setup, 118-120 decibels is .22 LR subsonic ammunition with a good suppressor level of noise.

If I have misunderstood something, I would love to be educated. But my understanding is that it was a rhetorical point.

I certainly won’t be wearing hearing protection when dry firing.

 

[Billy Goat]

In context, some people were reporting numbers that were highly unlikely. To make a point, Form showed that a meter could register that loud from just the firing pin dropping. And the rifle in question was clearly much, much louder than that.

From what I have read and heard, the meters, even very good ones, start to get really janky below 130 decibels. So, unless you know it was recorded in a proper setup with the best equipment, be skeptical of readings below that point.

When measured on a proper meter with a good setup, 118-120 decibels is .22 LR subsonic ammunition with a good suppressor level of noise.

If I have misunderstood something, I would love to be educated. But my understanding is that it was a rhetorical point.

I certainly won’t be wearing hearing protection when dry firing.

So its fair to say 120db for a dry fire is bullshit then correct?

 

[Q_Sertorius]

So its fair to say 120db for a dry fire is bullshit then correct?

Yes. Until Pew Science or the TBAC Summit record it, I would not rely on that number.

 

[Formidilosus]

So its fair to say 120db for a dry fire is bullshit then correct?

Yes. Until Pew Science or the TBAC Summit record it, I would not rely on that number.

No, not really. On true subsonic that meter 118-122 dB at SE- you can hear the firing pin. Whether the dry fire is precisely 120 dB or not isn’t the point- the point is that at 120dB you can hear the firing pin fall.


Shooters ear is 6” to the right of shooters right ear.

 

[Billy Goat]

Whether the dry fire is precisely 120 dB or not isn’t the point- the point is that at 120dB you can hear the firing pin fall.

I'm not really following this.


Why does it not matter?


It seems its getting repeated that (x) is this loud, so can't be this...

You are saying that it registers with other noises that it's a pulse that still shows and is very close?

It's a sound that registers just slightly before a suppressor I assume?

 

[Ucsdryder]

Anybody with access to the equipment could drop the firing pin on a spent case and see what the reading is. That might tell us if the 120 is the firing pin or something else. @TandKHunting it’s for science!

 

[alexnelon]

Anybody with access to the equipment could drop the firing pin on a spent case and see what the reading is. That might tell us if the 120 is the firing pin or something else. @TandKHunting it’s for science!

FYI, dropping the firing pin on a spent case will be noticeably less loud than actually dry-firing on an empty chamber because the primer is super soft and will keep the firing pin from striking the body of the bolt.

 

[HuntHarder]

Using my ZG7 on a .223, I can hear the firing pin drop when I shoot it. It's noticeably different than using other louder cans.

 

[Ucsdryder]

FYI, dropping the firing pin on a spent case will be noticeably less loud than actually dry-firing on an empty chamber because the primer is super soft and will keep the firing pin from striking the body of the bolt.

Correct, but the poster above said you can hear the firing pin on subsonic, so a round in the chamber, not an empty chamber.

 

[alexnelon]

Correct, but the poster above said you can hear the firing pin on subsonic, so a round in the chamber, not an empty chamber.

Yeah that's a waste of time it's nowhere near 120dB.

 

[Billy Goat]

Yeah that's a waste of time it's nowhere near 120dB.

Thats what my thought is, but I have seen that pop up several times. I'm trying to understand it.

 

[RockAndSage]

On true subsonic that meter 118-122 dB at SE- you can hear the firing pin. Whether the dry fire is precisely 120 dB or not isn’t the point- the point is that at 120dB you can hear the firing pin fall.

Not sure if it's because of doing a million dryfires, but I never made that connection that hearing the firing pin drop would also mean it was at 120 dB. There must be something in the nature of the duration of the sound that's keeping it from causing ear-ringing after hundreds of reps.

Any idea what dBs the actions of a cycling AR or pistol with subs comes in at?

 

[alexnelon]

Thats what my thought is, but I have seen that pop up several times. I'm trying to understand it.

My only thought is that maybe the point was that a suppressed firearm measuring at 120db is not so loud as to completely obfuscate the sound of everything else that occurs during the firing event.

I can't imagine that anyone could have meant that the firing pin striking a primer (insulated by like a half inch of steel) is actually generating 120dB impulses. That's like hammer on anvil level noise.

 

[RS_Non-Res]

two things going on here:
1) Is the firing pin noise 120 dBA?

No. Rock concert/chainsaw is 120 dBA.
Bolt action firing pin is probably closer to 60 (wild ass guess)
AR is probably 80 b/c spring and bolt noise (again wag, but still way less than 120)
Google is your friend

​

2) Can you hear the firing pin? Yes.
It's easy to conceive of gun noise as made of :​

Machine noise - minimize this with a bolt action instead of semi-auto
Muzzle blast - minimized by a can​

Sonic crack - minimized by subsonic ammo.​

A great can and subs leaves only machine noise.

The action noise on "my" Rascal 22 and a hole in the paper is the only evidence I have that it has fired.​

That action noise is a bit more than just the firing pin hitting the primer, there's also trigger noise and the striker spring, and pin stops too.

I'm wondering if what Form is saying is that when the muzzle blast (with a can) is measured at 120 dB, you can also discern the action noise. That doesn't mean that the action noise is 120 dB by itself. ​