I've seen some discussion on this forum about suppressors, and I did a search to look back, but I don't see enough specifics about noise suppression in say a .458 caliber. Perhaps the 458 socom is a good example of a rifle/cartridge that suppression is a worthy consideration, especially since they make factory loads that are speciffically sub-sonic, hard cast and solids.

I have read that the larger the bore the more difficult to suppress the muzzel blast. Could someone explain this?

Also, I keep reading the word sub-sonic. OK does this mean (5280x761/60/60 = 1,161 FPS) ??

Thus, a bullet traveling FPS less than 1,161 is sub-sonic?

Thanks
KB

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Thus, a bullet traveling FPS less than 1,161 is sub-sonic?

Yes.

Can't help you with the other part, other than guess that it has something to do with the volume of powder being burned in a larger case.

I have heard a 'silenced' shotgun firing slugs and it was silent! They say that a 'silenced' 44mag carbine is silent. Small powder charges and large bores to absorb the volume? Also to consider is the larger the bore the larger the baffle orifices are. (I'll be experimenting with larger case suppression when I get my 375/303 up and running. In the meantime, my 303 Brit is quite a bit quieter with a single baffle over barrel suppressor/muzzle break. Recoil is un-noticeable. It sounds like a 22WMR).

A 357 rifle shooting 190 gr lubricated lead bullets loaded in a 38 Spl case, mag rifle primer and 1.25 gr bulleyeys will go about 550 fps dead silent. A .458 with a 500 gr lubricated lead bullet and and only about 6 grs will get you down to the sound of a pellet gun. You need a heavy bullet vs. bore in order to have complete combustion and cooling and shrinking of gasses prior to the bullet leasving the muzzle. You need lubricated lead to keep frokm sticking the bullet in the bore. With jacketed bullets, the charge it takes to overcome friction and get the bullet down the bore is right at what it takes to get the gasses supersonic at exit (bang). The bang you hear on firing normal ammo is the gas breaking the sound barrier. The crack you hear later is the bullet breaking the sound barrier. You need to get both below the sound barrier to get quiet.

I would get on the phone to Gemtech and maybe a few others and see if the .45ACP cans will hold up to what you want to do. The nice thing about the pistol cans is thay are aluminum and light.

Yes, subsonic is below 1100FPS and it's very important.

I have a .223 Gemtech M4 pirrana can and almost feel like it was a waste of money. The sonic crack of the round going off makes my AR-15 sound like a Ruger 10/22. It's quiter, but not quite.

Terry

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The sonic crack of the round going off makes my AR-15 sound like a Ruger 10/22. It's quiter, but not quite.

Have you fired it with and without the suppressor to hear the difference? Sometimes I think my 'silenced' 303 and 303-25 are loud until I hear an unsuppressed gun firing!

I went the other way and just built a 45 acp rifle and use the sub gun supressor for a mack 10 on that. gemtech has a new one that looks real promising

a 44 special ruger works great also.

Don't know if this might be interesting to anyone else...

On mufflers for infernal combustion engines, there is a "relationship" between engine displacement and muffler volume to achieve a desired spl (sound pressure level, or amount of loudness, usually expressed in decibels (db)).

I would suspect there is a similar relationship in firearms suppressors....?

I would say so, yes. But it is not that straight forward since the aim in an infernal combustion engine is to evacuate the cylinders as quickly as possible whereas in a rifle 'muffler', one wants to restrict the flow of gasses as much as possible. This will be made more difficult with a larger bore for obvious reasons - unless the case or powder volume is small like the 44 mag or 45 ACP. But it is still possible to remove the muzzle blast altogether and have only the supersonic crack of the bullet. The problem with baffles in a suppressor is that they whistle! Loudly!

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the aim in an infernal combustion engine is to evacuate the cylinders as quickly as possible

That is only if you want to talk cylinder scavenging philosophy (usually regarding efficiency and specific output).
I am not talking about that. Only muffling.

interesting thoughts..
the 458 socom is designed to be suppressed, and the 458 whisper, of course..

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Originally posted by 303Guy:

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The sonic crack of the round going off makes my AR-15 sound like a Ruger 10/22. It's quiter, but not quite.

Have you fired it with and without the suppressor to hear the difference? Sometimes I think my 'silenced' 303 and 303-25 are loud until I hear an unsuppressed gun firing!

Oh yes, there is a difference. I was just hoping for more of one.

I've got a .22RF can also that I put on 3 different guns. Talk about fun When I screw it on my Savage bolt gun with the 20" barrel all I hear is the firing pin and the bullet hitting the target. I bought the .22LR can 1st so I guess everything else will be somewhat of a dissapointment.

Terry

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I bought the .22LR can 1st so I guess everything else will be somewhat of a dissapointment.

Ah! Yes... I know what you mean! But then I heard my tiny little muzzle device against a very large and expensive suppressor and there was no difference! Then I heard a fair size overbarrel suppressor on a 223 and it was like a 22LR being fired! That was impressive. Now I know it can be done! I also know that recoil can be reduced at the same time to the point where it is un-noticeable! (303 Brit - they don't hurt to start off with but without due care they smack one on the forehead with the scope and I cannot see the bullet strike. Now I can and I don't even think of rifle hold. All I need are foam earplugs.)

Even though my suppressed 458 socom ar-15 has s smaller powder charge, larger silencer and is subsonic, it is noisier than my ar-15 in 223 with supersonic ammo. I think it is due to the much larger bore of the silencer. My 458 is not hearing safe.

http://www.sengpielaudio.com/c...lator-speedsound.htm

The speed of sound at sea level at 0F is about 1051 fps, at 68F it is 1126 fps, at 100F it is 1160 fps.

Ranb

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Originally posted by TC1:I bought the .22LR can 1st so I guess everything else will be somewhat of a dissapointment.

Terry

Maybe, maybe not. Shoot a fairly powerful cartridge like the 223, or 308 at a metal plate. The loud clank will sound very satisifying when using a silencer.

Ranb