Information on why 9mm can be quieter than .45

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Lucky

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I've read here that 9mm's can be suppressed better than.45s, and the reason given was the smaller hole for gas to get out of.

Is there any manufacturer information on the matter? At the very least is there a manufacturer with 2 similar models, and an advertised lower reduction for the .45 can?

How can we know that it's the smaller hole making the can quieter and not the smaller amount of powder in the 9x19 case?
 
I'm sure if you slowed down a 9mm enough (ie same speed as a 45) it would be quieter than a 45 but at their respective speeds a 9mm would generally be louder.
 
muzzle velocity and powder charge are the major players here. You were right in your thinking, regardless of what you read. Anecdotal evidence is no match for emperical evidence. Did you look around www.silencertests.com?
 
I once heard that, after the bore size increases past .38" in Diameter, the sound gets much harder to muffle, because the something-or-other increases in an exponential, rather than linear, fashion.


But I read that it a gun rag, so... well, you know.
 
Ugh typed a long reply and got posting error.

Basicly it has to do with bore diameter. The wider the bore the more difficult it is to restrict the gas, and a larger amount will exit behind the bullet in the form of noise.

However 9mm tends to be a faster round, and once a round goes past the speed of sound it creates vibrations that are still heard in the form of a crack.
Some silencers counter this by using wipes that slow the bullet, reducing velocity and energy of the bullet as a result. Others use subsonic ammunition which generaly has lower energy, and very poor trajectories.

The .45ACP however is generaly subsonic from the factory, and does not need to be slowed or use special loadings to achieve its suppression potential.

So bore diameter plays the biggest role. The larger the hole in the center the more sound waves bypass the supressor and exit behind the bullet.
 
Yea forget about sonic booms and stuff, just muzzle noise. I was on another forum and they were wondering why FNP90s were suppressed so often, and I suggested it might be the smaller hole thing. Now I've been called on it and need source to back it up. I'll check that site thanks.

So bore diameter plays the biggest role. The larger the hole in the center the more sound waves bypass the supressor and exit behind the bullet.
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I just need that from an authority and it's good.
 
Here's an interesting thing about supersonic bullets and the noise made by them. The only public rifle range around here (that I know of) is ALWAYS hot. When you want to put up/change targets, you walk down an 8 to 10 foot deep trench with trenches at 25, 50, and 100 yards (think WW1). I know. It sorta freaked me out the first few times I was there too. Anyway, while out at the 100 yd trench, you can hear bullets passing by before you hear the muffled boom of the rifles. They sound like a reasonably loud "snap". I've taken out my earplugs and have'nt found the noise to be bothersome. It's nowhere near what it used to be like when the local SAC base's 102's would go transsonic. Size does matter though. I had a friend shoot my 450 Marlin and my 22-250 while I stood several lanes away from my lane (in the trench) and the 22-250 was much sharper (at nearly mach 4) but the 450 was louder (at a little less than mach 2).
Thought you might find this interesting.
 
Wasn't part of the reason for 147gr 9mm to get them subsonic for canned applications (and better penetration)?

6mm and .308 at 900m makes my ears ring when it goes overhead.
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:uhoh: I'll take your word for it!
 
.308 at 900m is got to be pretty close to going transsonic, depending on the individual rifle/cartridge. I've heard plenty of rounds go past at 300-400 yards, and the noise definitely isn't painful.
 
The 9mm round is actually more difficult to suppress than the .45 due to the fact that MOST 9mm rounds are supersonic while the vast majority of .45 is subsonic. If you allow a round to travel at supersonic speeds, a ballistics crack will be heard. This crack is loud enough to negate the usefulness of fiting your weapon with a suppressor.

If you fire a 9mm round through a wiped unit, the Hush-Puppy for example, the accuracy of the fired round is degraded because the round is making physical contact with rubber wipes as it exits the barrel. Therefore, wiped units are only good for extremely close range work.

The only reliable 9mm rounds that are suitable for reliable firing through a 9mm handgun suppressor, IMHO, is the IMI 158 grain subsonic. It is subsonic, HEAVY and it is extremely accurate, BUT your weapon will take a beating with this round.

IMHO the .45 is the only suitable caliber for pistol suppression. It is BIG, HEAVY, ACCURATE and SUBSONIC.
 
^^^Have you ever been around suppressors?

I own several. The .45 is significantly worse through a can, but it doesn't entirely have to do with the bore size. It has to do with the RATIO of the bore diameter to the CAN diameter, ie the useable volume of the can. Pistol cans can only be a certain size before they become impractically unwieldy. 1.375" is about the maximum diameter you can use well on a pistol, and is what's used on almost all .45 cans and many 9mm cans (many also use 1.25").

The bore size on a good .45 can is actually about .500". That's 13% of the diameter of the can. A 9mm bore is about 0.400", or 8% of the diameter (10% on a 1.25" can). The .45 cans have less useable volume. If you could make a .45 pistol can where the bore was 8% of the diameter, it would probably sound about like a 9mm can, but its outside diameter would be 1.77" - way too big for a pistol.

EVERY .45 pistol can on the market has to be shot with ablative media to be reliably hearing-safe, even the $1200 Knights Armament unit. On the other hand, EVERY 9mm can on the market is hearing-safe dry with subsonic ammo. That's because 9mm is easier to suppress well.

Further, subsonic 9mm is widely produced and available everywhere. I bought my last batch at walmart. Any 147gr 9mm will be subsonic from a pistol barrel. They cycle suppressed 9mm pistols with boring reliability. Not sure why you think IMI 158gr is the only suitable round.
 
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