I’m relying on the SIGforum Brain trust to help sort this out.

Many of us have tirelessly experimented to find what ordnance from what firearm give the lowest sound signature when using a certain suppressor. I’m relatively new to the suppressor party, and would appreciate some starting help.

These are just the normal rounds I am trying to fire at subsonic speeds to avoid sonic booms:

.22 ACP -Standard 36gn-40gn -SilencerCo Specter II (22lr)

9mm -Standard 147gn Ball ammo -SilencerCo Octane HD .45 ACP

.40 S&W -Standard 180gn Truncated Nose - SilencerCo Octane HD .45 ACP

.45 ACP -Standard 230gn Ball ammo - SilencerCo Octane HD .45 ACP

.308 -Standard 149gn -SilencerCo Omega (762X51)


As you can see from the list, most of these choices aren't going to work subsonic.

What changes do I have to make to my list in order to fire these calibers subsonic?

Are any of these rounds naturally subsonic?

What brands/grains/loadings work for you to achieve subsonic firing?


H&K-Guy

.22LR - just buy the standard velocity or subsonic loads.

9mm 147 standard should be subsonic in pistol.

40 180 should be subsonic in a pistol.

.45 subsonic.

.308 149 No, supersonic.
http://rifleshooter.com/2014/1...velocity-28-to-16-5/

Speed of sound 1,125 fps.

quote:

Originally posted by H&K-Guy:
Are any of these rounds naturally subsonic?

Some are. Subsonic means that the bullet travels less than the speed of sound. Under “standard” atmospheric conditions, sound travels about 1125 feet per second. Find a load that drives its bullets below that speed and there will be no supersonic “crack.” That assumes, though, that the temperature isn’t lower and the speed of sound is lower as well. In a calculation I was doing earlier for my location, the speed of sound was closer to 1080 fps.

Most 45 ACP loads are subsonic. Most heavy bullet 9mm loads are subsonic. Some 40 S&W is subsonic; some isn’t. No standard 308 Winchester load is subsonic, and trying to find or manufacture accurate loads that are is pretty much an exercise in futility in my experience. The 300 Blackout cartridge is available in many subsonic loadings.

Based on what I’ve read, the quietest guns are chambered for 22 Long Rifle with subsonic ammunition.

quote:

Originally posted by sigfreund:
Based on what I’ve read, the quietest guns are chambered for 22 Long Rifle with subsonic ammunition.

Bingo. Especially a longer barreled bolt action 22lr rifle with a good can. Pistols and semi-auto 22lr rifles are louder.

quote:

.308 149 No, supersonic.
http://rifleshooter.com/2014/1...velocity-28-to-16-5/



Speed of sound 1,125 fps.

Clicks link...cool. Why is that rifle propped against a chop saw?

Scrolls down...OMG!!

quote:

Originally posted by dusty3030:
.22LR - just buy the standard velocity or subsonic loads.

9mm 147 standard should be subsonic in pistol.

40 180 should be subsonic in a pistol.

.45 subsonic.

.308 149 No, supersonic.
http://rifleshooter.com/2014/1...velocity-28-to-16-5/

Speed of sound 1,125 fps.

The speed of sound is dependent on altitude and temperature. Generally, I use 1050 as a ceiling to ensure I'm subsonic in all weather & at all locations.

If you really want quiet fun, add a blackout bolt rifle to your list. Ruger makes one that's like $350 and is tons of fun. Also lots of fun in an ar, though not quite as quiet due to action noise.

According to everything I’ve read, the speed of sound in air is mainly dependent upon the air temperature, with only minor effects due to pressure (elevation) and humidity. The speed of sound in an ideal gas is dependent only on its temperature.

https://en.wikipedia.org/wiki/Speed_of_sound

http://www.physicsclassroom.co...2/The-Speed-of-Sound

https://www.grc.nasa.gov/www/k-12/airplane/sound.html

Good info above.
I'll add this:
I have an Octane 45HD and I use it on
45ACP (GLOCK 21)
40S&W (GLOCK 22)
9MM (converted GLOCK 23 & converted GLOCK 27)
300BLK (AR Rifle)
22LR (CMMG Converted AR15, Ruger MarkIII, Savage bolt rifle).

Yes, 230gr FMJ 45ACP is "naturally" subsonic.
180gr 40SW is subsonic. HUGE increase in noise level dropping down to 165gr in 40SW.
147gr 9mm is usually subsonic. I find 124gr fmj to be mostly subsonic, depending on brand. But it is on the cusp of supersonic and therefore more sensitive to air temp.
115gr 9mm, forget it...you're going to get bullet crack.

My quietest experience with the Octane 45HD has been on my bolt action Savage .22 rifle.

The 45ACP and 300BLK (subsonic only, the Octane is not rated for high pressure (meaning supersonic) rifle rounds) have about the same noise level. This is sort of expected since they have very similar ballistics w/r/t bullet weight and speed.

Oh, in case you are wondering.... All my conversion barrel for my GLOCKs came from Lone Wolf.

Here's a website that lists some FPS from various manufacturers on different calibers.

Ballistics 101

For .22 LR, the best and most consistent performance I've gotten has been Gemtechs' orange-box subsonic. It's actually loaded by CCI.

Federal also makes dedicated subsonic .22LR, sold in black boxes.

Most .22LR match ammo is subsonic as those little bullets do weird things when they transition from super to subsonic.

Federal also makes dedicated 9mm subsonic ammunition, but most if not all 147 gr or greater will be subsonic.

S&B makes subsonic .308, but you'd better be shooting it out of bolt gun because it will not cycle any semi-auto action that I know of. It comes in green boxes.

.40 is not very popular in my area, so I don't know of any dedicated subsonic commercial ammunition in that caliber.

.45 ACP is probably the most naturally subsonic because that caliber has always been the domain of the slow-and-heavy crowd (the opposite camp would be something like .357 SIG).

Of all those calibers, subsonic .22LR has been the only one that is truly party-trick quiet.

When I shoot my .22 AR upper with Silencerco Warlock at local speed-steel matches, everyone takes off their ear pro. I do have to remind myself to remind the RO to tap the timer with his knife when I'm done--no way it's going to pick up the signature. But the best setup I have for subs is my PWS Summit--straight pull bolt w/ suppressor & subs is quieter than the staple gun I use to put up targets.

If you want to shoot subs in a rifle buy rounds with that set of skills and a rifle set up to shoot them. An accurate 308 is hard to do with subs because most rifles are set up to shoot supers accurately. You need a 300 blackout, 458 socom or other rounds built with the idea they would be surprised.

Thanks guys. Excellent information!

With your help, I have discovered some of my problems.

Fail #1: First, my Federal Value Pack, 36gn .22lr rounds are traveling at 1260 fps. I need to try to stay under 1050ish to be successful.

Fail #2: My Blazer Brass 9mm rounds appear to be higher velocity 124gn bullets instead of the NATO 147gn bulk surplus ammo I thought I was using. Again, I need to find some 147gn slower ammo to be subsonic. With this, I should get somewhere around 130.4 DB.

Fail #3: Yet again, I failed to realize I will only be able to go subsonic with 180gn bullets, or there abouts. (Thanks hudr). That should get me down to 130.6.

Fail #4: For some reason, my Octane 45 HD works great in suppressing a HKUSPF Tactical, but utterly fails when used on a Glock 30 with Storm Lake hardware. Both are using the same 230gn bullets. I haven’t figured that one out yet.

Fail #5: I actually expected more out of my Omega on the SCAR 17s, in fact to be quieter than what I was hearing. It turns out the Omega’s report with 762X51 only brings the sound down to 133.9, so no subsonic there. Also, trying to get subsonic on a 308 out of the SCAR17s just is not going to do it for me (Thanks LDD).

Thanks dusty, Sig, and Buc for your excellent links to some great information.

Win #1: The brain trust here is amazing. I’ve learned more from 10 posts than I could anywhere else. Now I can go to the range and look cool in front of the big kids! If there is any more great information you guys can come up with, please continue to school me.

H&K-Guy

Your fail #4 may have to do with the short barrel on the G30 and what has to happen with the action (geometry, physics, steam pressure and fairy magic) to make 45ACP work in such a relatively small firearm.
Kinda related, but not really, and I have not tried this myself, but....I saw a YouTube video with a G19. A fella was able to quiet it down a bit more by putting in a stiffer recoil spring. This kept the action locked for a fraction of a second longer, therefore allowing more time for the gas to flow into the suppressor instead of leaking out of the breech as the action unlocked.


And yes, the knowledge amassed here is awesome and it covers EVERYTHING, not just firearms.

BTW, back to suppressors....I'm still learning also.

quote:

Originally posted by H&K-Guy:

Fail #4: For some reason, my Octane 45 HD works great in suppressing a HKUSPF Tactical, but utterly fails when used on a Glock 30 with Storm Lake hardware. Both are using the same 230gn bullets. I haven’t figured that one out yet.

http://www.silencertalk.com/fo...iewtopic.php?t=36647

quote:

-A subcompact GLOCK doesn't suppress well.

quote:

A GLOCK 30 is a sub-compact, and as a result, it doesn't work well with suppressors.

After the last round is fired, the slide locks open. When the gun is like this, look at the barrel and it is tilted upward - this is true for all GLOCKs (except possibly one in .380). However, the smaller the GLOCK, the more extreme the angle on the barrel. If you look at one of the GLOCK 17L models - 9mm, long slide for competition - you'll see that when it locks open on the last shot the angle is very, very mild compared to the angle of any of the sub-compacts.

Imagine if a silencer was attached to your gun - the suppressor would stick way up into the air on the last shot... or have to raise that high between each shot before returning to the parallel position. That just won't happen. Instead, if you put a heavy object like a suppressor on the sub-compacts, instead of waving the object around, the gun just doesn't cycle. You pull the trigger, the gun fires, the suppressor works, it is quiet, but the gun doesn't cycle. So you have to reach up and pull back the slide manually between each shot in order to eject the spent brass and chamber a new round.

If you want a GLOCK to fire reliably, you'll need to get the next size up.

Silencertalk is a solid resource. Anything thought of being done with a suppressor has been done and the results posted and vetted by a very experienced and knowledgeable membership. They're the sigforum of suppressor forums.

Keep reading and trying it out. I recommend getting a chronograph if you're making the loads yourself or trying to find the right 180 gr ammo. Personally, I wouldn't bother with .40 S&W. Had I read silencertalk sooner, I'd just get a 9mm suppressor because I got a .45 thinking it would be so great to shoot .40 suppressed. For pistol rounds, 9mm is all I shoot suppressed. Good luck!

You can try these 158gr 9mm subsonic rounds.