Moderated 17HMR Sound Test.

[Frenchieboy]

There has always been a lot of questions about how effective moderators are when used on a 17HMR Rifle. Several people (myself included) have on occasions shot rabbits with a moderated 17HMR only to find that there are other rabbits close by that don't appear to hear anything even though the shooter does hear quite a loud "sonic crack" which you are very unlikely to ever get rid of completely with a 17HMR.

With that in mind I went up to one of my permissions to try to find out what noise (If ant) actually reached a target at about 80(ish) yards when fired at with a moderated 17HMR. This was an ideal time to check as I had just stripped and cleaned my moderator and the barrel of my 17HMR and I needed to put a few "fouling rounds" through it and then re-zero it.

The results do leave a little to be desired as the sounds picked up by the camcorders were muffled and interfered with by the wind noise which my camcorders seem to favour. I will try again to find a more conclusive answer to the question when I have some spare time on a windlewss day!

In the mean time you decide! Here is the video:

 

 

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[toolazydecoy]

very interesting, i was surprised howlittle difference the mod made to be honest, good video

[ollie]

could hardly notice the difference between Mod and without. There was still the 'Pop' that you talked about.

[Frenchieboy]

Unfortunately these results could be a little misleading due to the wind noise muffling and interfering with the true sounds. That situation is compounded due to the fact that the wind was blowing from the firing position straight towards the POI which meant that ANY sound made at the firing position would be carried right up to the POI. (Bad planning on my part) To be honest I am not sure that these results are very true or accurate, the test really needs to be done again on a windless day to get more reliable and accurate results to judge!

Edited August 6, 2010 by Frenchieboy

[toads]

Hi, very interesting ,but I agree a still day would be of more value for this test.Do you get many up in them hills?atb

[night owl]

the only true way would to be to use a decibell meter

[Frenchieboy]

Hi, very interesting ,but I agree a still day would be of more value for this test.Do you get many up in them hills?atb

You would be surprised at what I come across up in them there hills mate!

On a serious note, yes, there are no end of rabbits in that area! It would not be an exageration to say that I have shot somewhere in the region of 250 to 300 rabbits in that (70 acre aprox) area over the last 9 months. There are also a few Badger Sets that I am watching for photographic reasons and also a large Fox Earth that has several resident foxes in it. These foxes do not sem to be causing any concerns for the farmer so there has been no request to cull them so they are quite safe for the time being!

On the whole it is a very good area for rifle shooting as there are no end of safe backstops, so much so that the only time I can not safely take a shot is if the quarry is right on the sky line. Another beauty of this area is that it offers some remarkably safe areas for "long range zeroing and shooting" as I can, as long as I chose where I shoot from, see anyone that is on any of the few nearby footpaths before they got to within 200 yards of the firing line!

[bigstevouk]

Well done, could you do one with your 222 ......

[ricky green]

There has always been a lot of questions about how effective moderators are when used on a 17HMR Rifle. Several people (myself included) have on occasions shot rabbits with a moderated 17HMR only to find that there are other rabbits close by that don't appear to hear anything even though the shooter does hear quite a loud "sonic crack" which you are very unlikely to ever get rid of completely with a 17HMR.

With that in mind I went up to one of my permissions to try to find out what noise (If ant) actually reached a target at about 80(ish) yards when fired at with a moderated 17HMR. This was an ideal time to check as I had just stripped and cleaned my moderator and the barrel of my 17HMR and I needed to put a few "fouling rounds" through it and then re-zero it.

The results do leave a little to be desired as the sounds picked up by the camcorders were muffled and interfered with by the wind noise which my camcorders seem to favour. I will try again to find a more conclusive answer to the question when I have some spare time on a windlewss day!

In the mean time you decide! Here is the video:

 

 

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type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>">

name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="

type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>" type="application/x-shockwave-flash" wmode="transparent" width="480" height="385">if the bullet travels faster than the speed of sound,somewhere in the region of 2500fps,i believe,the rabbit you are shooting wont here a thing,and they dont pick up the direction of the noise as it is diffused with a mody on.when you miss the odd one dont you find that they sometimes run towards you??good vid tho.try a bit of thinish foam over your mic,should help with the wind noise..

[deputy dog]

Interesting vid frenchie mate. But if you are as accurate hitting them bunnies as you are hitting them targets. I don't think mr Bunny is going to hear any thing after the 17grain head goes through his ears lol. :o

[malkiserow]

Good vid Frenchieboy. I guess the sound is all about the bunnies little friend next to him for your second shot. In the second part of the vid I thought the rifle pop was gone but could just hear the 1 pop as you hit the ground. So does the .22LR bullet make less of a pop when it hits the ground with its much lower energy....? I wonder what real difference a bunny hears?

[Gonk]

Good stuff Frenchieboy, interesting results

[ash243]

I have been thinking about this since I looked at the video and I have done a bit of thinking and some research on this yesterday and went for a play with some different rounds and rifles and I have these are my findings and thoughts and in no way a go at Frenchey .

 

The target end shots

 

One of the first things is that the video on the target should have been in front of the target with the round passing over the top of the video camera

As I believe that the sound you are hearing on the video is the impact of the round on the target and then the backstop

Some on here have said that you need a decibel meter this cant work because a meter will only measure the peak sound "pressure" noise, not the duration or frequency. Decibel meters are limited to the highest point of the noise if I draw a comparison between my standard 308 and my mates 300win mag. Any meter would show that both produce the same level of noise when fired but you can detect a noticeable difference and that the win mag sound much louder. What the dB meter show is the both produce the same high peak sound but the Win Mag hold the peak for longer where the high peak on the 308 fall away faster.

 

In most tests I did yesterday with a .22LR simply because I had a large selection of ammunition in the safe the moderator reduces the sound level down from and average of 160 dB with High velocity rounds to as low as 117dB and 125dB down to 85dB for Sub Sonics (in the health and safety at work act they many on restrictions on noise there is maintained exposure over time or sudden noise over and above 95dB for the first Action level) Comparatively, ear protection commonly used while shooting provides 18 to 32 dB of sound reduction at the ear. As a comparison, chainsaws, rock concerts, rocket engines, pneumatic drills, small firecrackers, and ambulance sirens are rated at 100 to 140 dB

 

The shooting point Shots

 

The camera on the shooters end was picking up, multiple sounds when the trigger is pulled. Most article on suppressors I have read refer to the 5 categories of noise as: action, blast, sonic signature, impact, and operator. Though some of these will change depending if the rifle use is bolt action of semi auto

In order of timing

1, Action noise required to ignite the round.

2, Muzzle blast resulting from the discharge of propellant from the end of the barrel.

3, Sonic signature of the projectile in flight.

4, Action noise in some firearm variants as the spent round is discharged and a fresh round reloaded.

5, Impact noise created as the projectile finds terminal impact.

 

The calibre and power of the bullet/cartridge being suppressed is also an important factor. i did notice a large difference in the 243 with a 95 Grain SST loaded with 33.7 grains of Hogdon 4895 and the same head and case and primer but with 70 grains of Hogdon 870 i did find that, equal quality suppressors can quiet the report of a smaller calibre bullet more effectively than a larger calibre bullet. This is because the exhaust gases can move more quickly through the exit hole necessary for larger calibre bullets.

 

As we all know there are many advantages in using a Moderator that are not related to the sound.

I find using centerfire rifles and moderators bring me important benefits that outweigh the extra weight and in some cases resulting change in the firearm's centre of gravity. The most important for me is the hearing protection for me as well as my companions.

 

The others reducing, recoil and muzzle-blast and muzzle Flip, it also allows me to follow-through calmly a further carefully-aimed shot without delay if necessary.

 

The target spices Deer rabbit fox etc are often confused as to the direction of the source of a well-suppressed shot. In the field

 

The down side for me as a stalker ever, the comparatively large size of a centerfire rifle suppressor can cause unwanted noise if it bumps or rubs against vegetation etc, I do have a neoprene cover but I wish I could get a black on as I don’t like DPM. .

 

My conclusion is that the My Moderator works for me to protect my hearing. I don’t think that the intended target hears the movement of the bullet or the sonic blast I think it hears the miss of the bullet hitting the back stop and this thud is what alarms them.

 

As I said these are my thoughts and findings please feel free to comment and yes I am that sad that I have a decibel meter at home but thats another story.

 

all the best ash

Edited August 8, 2010 by ash243

[Frenchieboy]

All your comments and observations as being quite right Ash, and I am most certainly not offended by anything that you have said. I only carried out this little "experiment" as I was a bit bored and did not put anywhere near enough thought into it. The main point is that it has really got me thinking now and even though I do not have the luxury of a Db meter of anything like that I believe I can get better results with a little thought and better weather conditions.

There are several things that I will do differently on the next "test/experiment":

1. I will chose as windless as possible a day and set myself up with whatever wind there is blowing into my face the same as we would ideally like the wind when out in the field rather than blowing towards the target area.

2. I will set the first video camera up on a tripod next to the rifle rather than have it mounted on the rifle where it is picking up every little sound.

3. I will place the (Target End) camcorder facing the shooter but a short distance (Maybe 5-10 yards or so) in front of the target so there is less chance of it picking up any of the noise from the bullet impacting into the ground - Ideally it should only pick up the sound of given off by the rifles report and the sound of the bullet travelling overhead.

4. I will try to find some way of "surpressing" the ambient sound of what wind there is by shielding the microphones on the camcorders with a bit of linen or foam.

I realsie that this will still not give scientific quality results but hopefully it will simulate what if anything a rabbit hears when a moderated 17HMR is fired near it.

I expect to be doing this towards the middle of the week as I am just about to leave home with the 17HMR to get the barrell shortened, re-crowned and re-threaded and will have it back on Tuesday (Hopefully)!

[paulthekiller]

Good video Frenchieboy & good grouping on the target as well keep it up

[b682]

Good work,

 

But if you hit the rabbit, it will hear nothing as the speed of sound is 330mtr/sec and the bullet is travelling a lot faster than the speed of sound -so the bullet will have killed the rabbit before it ever got opportunity to hear the gun go bang.

[Frenchieboy]

Good work,

 

But if you hit the rabbit, it will hear nothing as the speed of sound is 330mtr/sec and the bullet is travelling a lot faster than the speed of sound -so the bullet will have killed the rabbit before it ever got opportunity to hear the gun go bang.

 

If you had read the first parargaph of the original post you might not have needed to state the obvious! If you care to spend the time to check you will find that the first paragraph of this thread reads as follows:

"There has always been a lot of questions about how effective moderators are when used on a 17HMR Rifle. Several people (myself included) have on occasions shot rabbits with a moderated 17HMR only to find that there are other rabbits close by that don't appear to hear anything even though the shooter does hear quite a loud "sonic crack" which you are very unlikely to ever get rid of completely with a 17HMR."

 

I think this opening paragraph makes it quite clear that the "experiment" was carried out to find out what if anything a rabbit close by to another one that you shoot might hear from your rifle!

Now I realise that 10:31 might be a bit late at night for you but you really ought to think about what you are about to say before you make yourself look a bit of a plonker in future!

[wy111]

Any rifle fired, thats above 342 m/sec(Bl55dy hate metric, ok, speed of sound), it's obvious the target will not hear it before it's dead!

I don't give a monkey's about db meters. To the shooter, depending on wind direction, can mean next to no sound or a good un. With no wind, shooter hears minimal, at 90 degrees, slightly more, but down range, still the same "crack". Apparently, the "crack" is diffused with a mod, as with ANY rifle down range, so they are not sure where it came from or what to do. Why some run and others stay put? How longs a piece of string?

How many times do you go out lamping and rabbits squat till you nearly stand on them? They know you are there, but squat, feeling safe.

If like you say Frenchie, you are hearing the, maybe, crack, you must be working upwind, so you hear more, even with the mod, but the rabbit hears less.

Just my 2 penn'orth

Edited August 9, 2010 by wy111

[Frenchieboy]

I agree with all you say WV111. Personally I am not over worried about what if anything the rabbits hear as I still get my fair share both in daylight and on the lamp anyway. I only did this as a bit of an experiment to try to find out what the answer was (I did get a PM suggesting that I might like to try it). Like I have said in a previous post on this thread I did not put enough thought into it so I will try it again when I get my 17HMR back (Which should be today) just to settle my mind and that of others that were interested in knowing the answer!

I totally agree that when you are out in the field the wind direction is one of the most important thinks to take into consideration as it can make such a difference both noise wise and scent wise that it can make of break a days/evenings/ nights shooting!

[Gonk]

The PM was from me suggesting it and thanks to Frenchieboy for doing it. We all know the shot rabbit won't hear anything but what would the others close by hear, that's what Frenchieboy tried to show us. Wind speed, wind direction, weather and time of day all affect sound so it would be extremely difficult to capture all all these variables but what Frenchieboy showed us was a good insight and thanks again.

[pavman]

Well done FB i was only asking one of my land owners last week what they hear from the house about 80 yards from a rabbit shooting spot i shoot from, they said its still quite a loud crack so both the other Rabbits and the local ANTIS do get a warning when the HMR is in use

 

wonder how far the sound travels in normal conditions, to the point you cant hear it, as you know we have a few snipers who can drop bunies all day long over 200 yards