Subsonic 9mm or .45, does one suppress better than the other?

[gun'sRgood]

Out of curiosity, what are the differences between suppressing .45's -vs- sub 9's? Guessing here, but it seems the 9's would shoot "flatter" or have a greater ease of control than that of .45's? Also, I'd guess that the cyclic rate would be higher for the 9's? As far as the suppressor ? No idea.

 

[Demi-human]

Well, most 45 Auto is already subsonic, so that makes it an easy button.

I’m sure a nine has a flatter ballistic trajectory, but it would be the same with a suppressor with either one, unchanged.
Assuming both wear an identical muffler, the recoil reduction will be the same for each firearm. So the already lower recoil level of the nine will remain more controllable as compared to a 45Auto.

A recoil operated pistol will not increase its slide speed. In fact, the Nielsen device is a spring mount inside a can to enable slide cycling with suppressors on Browning style locking systems. The extra weight of suppressor, and the reduction in overall recoil, absorbs the energy that would be used to operate the pistol.

A 9mm PPC is blow back operated and the increased time of chamber pressure will increase the force on the slide/carrier, which will make it run faster. The same is true for a gas operated rifle, the increased letdown time allows more gas to push the carrier, which can increase cycle rate and also the felt recoil as the buffer crashes the back of the receiver extension.

Fun fact, a 45Auto Carbine can be gas operated or punishingly harsh, blow back operated.

 

[Englishmn]

In my personal experience subsonic 9mm is noticeably quieter than 45acp.

 

[8Ball_99]

9mm is going to be quieter. I mean there would be exceptions of course. If you were using a short k can for 9mm and a full sized good quality can for 45 then the gap might be close. But assuming the cans are equal quality the 9mm will be noticeable quieter. Which makes sense because the powder charge is larger in the 45. If you compare load data 147gr 9mm has almost half the powder as a 230gr. If loading your own you could close that gap some too. But still the min load for 220gr/230 45 is still above the max for 147gr 9mm.

Cans add back pressure. They just do. On a pistol that doesn't really equal recoil though. Infact they are softer shooting normally because like was mentioned above the booster absorbs some energy. Also just the can itself slows the gases existing the barrel which reduces recoil. On top of that your hanging a weight off the front of the pistol. More weight=equals less felt recoil. More weight out front equals less muzzle rise. You shoot the same pistol with the same ammo both suppressed and unsuppressed. It will be softer shooting suppressed. The extra back pressure might make the slide cycle faster/harder in some cases, but usually not with a booster. That's more of a problem with fixed barrel PCC and rifles. That's why a lot of rifles have adjustable gas blocks with a suppressor setting to help deal with the back pressure and the extra gas.

 

[Zak Smith]

I recently did a lot of 9mm pistol can testing. What we came up with is that the port pop from basically the top say 6 cans, shooting full power ammo (subs or supers) was about the same and was the loudest part of the report that made it to your ear. For all of them it was about 140-141 dB. When you got into HUSH or STELTH (ie, "extra sub" sub sonic), you could get that ear number down to like 132-135 dB because the port pop was reduced.

Our 45 data is very preliminary so I wouldn't quote myself on it, but it looks like the port pop is still in that 140-144 range with full power (subsonic) and with HUSH/STELTH, with the ear dB numbers in that 129-135 dB range. I know this makes it look like the 45 can be quieter at the ear, but without repeating some experiments I wouldn't bank on that small difference in dB.

The difference, though, is that the quietest 9mm cans (at the ear w/ HUSH/STELTH) from paragraph 1 are like 4-6" long by about 1.3-1.4" diameter, while the 45 cans in paragraph 2 are more like 1.375-1.45" diameter and in the 6-9" length range. So based on that, I would say even if the dB numbers were the same, the 9mm suppressed "better."



Here is a data table for comparison's sake

 

[Zak Smith]

Also, we found pretty much no difference in ear dB numbers for super vs. subsonic 9mm. The port pop dominates what you hear. Of course, you can hear the shockwave bounce off things downrange, but that does not contribute to the muzzle and/or port/gun report you hear.

 

[MachIVshooter]

9mm. Smaller powder charge, smaller suppressor bore.

Hosts make a big difference, though. Hammer fired guns with longer lock times like Sigs, 3rd Gen S&W, 1911s, etc. will be quieter than striker fired guns. I can shoot my 5906, 3906 & 92 FS without ears using subs and not be bothered, but all of the striker fired guns snap my ears. Same is true of 45s, I find my 1911s and S&W 4516 a lot more tolerable than the RP45, M&P or G21.

I do have to disagree with Zak on sub vs super ammo from a human ear standpoint. What the Pulse picks up might indicate it's not the loudest thing, but my ears can't handle supersonic handgun rounds. Where and how the shockwave propagates off the wide, slow, blunt bullets is highly offensive to me.

 

[Zak Smith]

When we get into impulse (area) measurements I'll update it on supers vs. subs.

Another tidbit, an HK USP9 Tactical metered about 2-3 dB quieter (ear) than a Glock 17 and HUSH/STELTH ammo. With full power ammo, the relationship was opposite.

 

[8Ball_99]

I do have to disagree with Zak on sub vs super ammo from a human ear standpoint. What the Pulse picks up might indicate it's not the loudest thing, but my ears can't handle supersonic handgun rounds. Where and how the shockwave propagates off the wide, slow, blunt bullets is highly offensive to me.

I feel the same way. You can measure sound with instruments all day long. It gives you an idea. But in real world use its different. Sonic Crack bothers my ears on most Firearms if I don't wear earpro. Now the dB rating at my ears might be in the safe range, but the tone and pitch is uncomfortable to me. Depends some on the firearm and caliber. But typically if I'm not shooting subs I still wear some kind of ear pro. Personally 9mm supers are some of the worst offenders.
I have the same experience with suppressors. Some sound better then others because of tone, not volume level. It's hard to explain, but one might be a little quieter and to me sound worse because of the type of sound.

 

[Zak Smith]

If you want an alternate takeaway from the same data, you could conclude that a 9mm or 45 will never be quiet at the ear (ie it will be about 140 dB or higher) if you are using full power ammo (super or subs), and that you need specialty "extra subsonic" ammo to get that ear number down close to 130 dB.

 

[8Ball_99]

If you want an alternate takeaway from the same data, you could conclude that a 9mm or 45 will never be quiet at the ear (ie it will be about 140 dB or higher) if you are using full power ammo (super or subs), and that you need specialty "extra subsonic" ammo to get that ear number down close to 130 dB.

I do think the load plays a big part, but you can have full power subs that are very quiet. I load my own and the dtype of powder makes a difference in sound levels. My 9mm subs are pretty quiet, but are still pushing over 980fps. Same way with other calibers. I shot some 300blks today out of an 8" pistol with subs. I worked up the load using a lab radar and they are barely subsonic at an average 1025fps. But are very quiet to the shooter and diffentily hearing safe. They are Sub x hollow points so I wanted the max speed while staying subsonic. They are just as quiet as my normal subsonic plinking load that's about 80fps slower. But those are slightly heavier bullets.

So yeah you can have full power subs that are still very quiet. But with the same type of powder diffentily the lighter charge will be quieter. You don't necessarily have to get a lower fps round to be quieter though. Same bullet traveling the same speed could be quieter just buy trying at different brand of ammo. Or if you load your own swapping to a different powder.

 

[Zak Smith]

I'd love to see legitimate scientific data that demonstrates those points.

 

[8Ball_99]

I'd love to see legitimate scientific data that demonstrates those points.

I diffentily don't have any scientific evidence. Lol. Just going off how it sounds to me and others. Could even come down to tone and pitch too. Like how some cans just sound better then others even if they aren't quieter. I know just the past weekend I had a buddy who had some Underwood ammo Sub 300blks. They wouldn't even cycle his rifle. I handed him a mag of my handloads and they were just as quiet to our ears. But they cycled his rifle and were still moving around 980fps. I didn't have the radar out. So I'm not sure what his ammo`s FPS was, but I'm assuming less cause of the cycling issues with his rifle. Not scientific at all, just four guys on the range going those sound the same, but one actually cycles the gun. And I just happen to know what mine are loaded to because they were handloads.

I have played with different powders in the same loadings and some just seem quieter then others even though they are moving around the same FPS. Maybe it has something to do with burn rates. I don't really know. I just know if you want this xxxgr bullet to move as fast as possible while staying subsonic. What powder you use does make a difference to how loud it sounds.

 

[MachIVshooter]

Some sound better then others because of tone, not volume level. It's hard to explain, but one might be a little quieter and to me sound worse because of the type of sound.

The tone (frequency) absolutely makes a huge difference, not just in perception, but actual damage potential. Lower frequency sounds at the same pressure level are less offensive and less damaging.

I've had many instances of cans that metered lower sounding louder.

Metering is very useful for development, but at the end of the day, I care what real ears in the wild tell me, mine and other people's. I have pretty sensitive ears, so generally if I don't find it offensive, I can bet on other people feeling the same.

Environmental factors make a big difference, too. Not to the meter, but for us, cooler, denser air and reflective surfaces nearby can take a sound that's perfectly tolerable out in an open field and make it downright painful. To that end, it's why the objectivity of metering equipment is important in development. We can only do so much to control our environments, and our ears can't pick up changes of less than 3-4 dB at the levels of suppressed gunshots, so incremental design changes that often make rather small differences do need that objectivity and precision. But I would never, ever select a can based on published SPL figures. It's not always the foremost priority anyway, but even if it is, dBs are not the whole story.

 

[N555]

9mm with subsonic ammo is definitely quieter than 45.
I found that if I load 45acp with really fast burning powder, say about 4.5gr of WST with a 230gr bullet going about 700fps they are almost as quiet as any subsonic 9mm.
Problem is most 45 hollow points don't open up at 700fps.