Why is the 45 so hard to quiet down?

bob332 · Post by **bob332** » Wed Sep 12, 2007 1:24 am

everybody says that the best pistol rounds (not including 22) to quiet down are 9mm, 40 s&w, 10mm and then 45 and 45 needing to be wet. why is this? is it the bullet design? case design? powders used for 45?

thanks in advance,
bob

stymie · Post by **stymie** » Wed Sep 12, 2007 1:34 am

BORE DIAMETER is a rather significant issue even though the round may be subsonic.

Tobi · Post by **Tobi** » Wed Sep 12, 2007 1:47 am

It is the large bore diameter in connection with the low gas pressure produced by the .45. And that is the reason too, why a muzzle brake for a 45 is not as effective than for a 38 SA i.e.

bob332 · Post by **bob332** » Wed Sep 12, 2007 2:24 am

ok, makes sense now

Golovko · Post by **Golovko** » Wed Sep 12, 2007 2:25 am

And the reason bore size is a concern is the same reason that dumping water out of a glass happens much faster than dumping water out of a bottle. It takes a longer amount of time for the gasses to force their way out of a small hole than out of a large hole.

bob332 · Post by **bob332** » Wed Sep 12, 2007 2:50 am

it makes sense, but even the difference between 40/10mm and 45? how do you combat this? make are larger can? goal is for a sbr/suppressed ar45 in the future...10" of can wouldn't be an issue....

Golovko · Post by **Golovko** » Wed Sep 12, 2007 3:27 am

Area of 9mm hole: 0.1000 square inches.

Area of .40 caliber hole: 0.1256 square inches.

Area of .45 caliber hole: 0.1589 square inches.

The .45 caliber hole is almost 27% larger than the .40 caliber hole and almost 59% larger than the 9mm hole. When dealing with area those numbers add up quick. Efficient baffle design and longer silencer bodies can help overcome the problems inherent with large bores. A wider silencer body helps too, but not as much as additional length. The bigger the silencer the more room there is for the gasses to drop in pressure and temperature before reaching the exit.

DISCLAIMER: The numbers used aren't based on actual silencer bore sizes, nor are they necessarily based on actual bullet diameter. However, they are adequate for illustrating relative area versus each other.

Dan · Post by **Dan** » Wed Sep 12, 2007 11:28 pm

bob332 wrote:it makes sense, but even the difference between 40/10mm and 45? how do you combat this? make are larger can? goal is for a sbr/suppressed ar45 in the future...10" of can wouldn't be an issue....

I would suggest getting an integral. The gas pressure is relatively high behind the bullet before it leaves the end of the barrel and can be diverted through a port.

Billmanweh · Post by **Billmanweh** » Thu Sep 13, 2007 9:28 am

"low gas pressure" meaning there's less gas pressure to be diverted? it seems like on some level that low gas pressure would be quieter.

ArevaloSOCOM · Post by **ArevaloSOCOM** » Thu Sep 13, 2007 9:30 am

I don't know.

I just know that the KAC can id hearing safe , dry, on a MK23 so i have no choice but to get that.

I was stunned to find out that most 45's cans have to be fired wet to be safe, IMHO that's nuts.

#93 · Post by **#93** » Thu Sep 13, 2007 12:23 pm

I think you will be able to get a 45 can for an AR that will be hearing safe dry. The key to the 45 is having a lot of volume. That is much easier on a rifle than a pistol.

The DeLisle carbine, many Camp 45s, converted Spanish Destroyers and the Rihnland Arms conversions are all examples of 45 long guns with suppressors that work well dry.

2 years ago at the ISSMC I met a fellow who just got a 45 suppressed upper for his M16. I did not get to hear it but IIRC SRT did the work.

Golovko · Post by **Golovko** » Fri Sep 14, 2007 1:37 am

Billmanweh wrote:"low gas pressure" meaning there's less gas pressure to be diverted? it seems like on some level that low gas pressure would be quieter.

Normally lower gas pressure would be better, but some silencer designs redirect some of the gas so that it crosses back through the main flow and causes disruption. Imagine taking two garden hoses and shooting the stream from one into the side of the stream from the other. Designs that rely on such an effect tend to work better with higher pressure gas because at higher pressures the turbulence caused by interfering gas flows is more violent. At lower pressures the turbulence isn't as violent, making it more difficult to delay the flow of gas through a given aperture without relying on additional volume in which to contain the gas. Having a bigger bore than that used for smaller-bore, higher-pressure cartridges just compounds the problem.

Low gas pressure isn't the only part of the equation. The amount of gas is important too. 12 gauge shotguns operate at well under half the maximum pressure than .45 pistols, but they produce a lot more gas.

Tobi · Post by **Tobi** » Fri Sep 14, 2007 1:59 am

Billmanweh wrote:"low gas pressure" meaning there's less gas pressure to be diverted? it seems like on some level that low gas pressure would be quieter.

Yes right, but toghether with the big hole and and not much gas at all it is hard to suppress with a normal sized can.

green0 · Post by **green0** » Fri Sep 14, 2007 8:44 am

ArevaloSOCOM wrote:I don't know.

I just know that the KAC can id hearing safe , dry, on a MK23 so i have no choice but to get that.

I was stunned to find out that most 45's cans have to be fired wet to be safe, IMHO that's nuts.

I have an Evo .45.

Nuts? I can shoot it in my backyard residentally. It's quieter than a pellet gun. There's nothing nuts about it.

The thing is like two DB's louder than KAC dry. big deal.

JPratt06 · Post by **JPratt06** » Fri Sep 14, 2007 9:45 am

green0 wrote:
ArevaloSOCOM wrote:I don't know.

I just know that the KAC can id hearing safe , dry, on a MK23 so i have no choice but to get that.

I was stunned to find out that most 45's cans have to be fired wet to be safe, IMHO that's nuts.
I have an Evo .45.

Nuts? I can shoot it in my backyard residentally. It's quieter than a pellet gun. There's nothing nuts about it.

The thing is like two DB's louder than KAC dry. big deal.

I assume you mean you can shoot it in your backyard wet

Dry would be too loud in my neighborhood. The houses are 10-20 ft apart, and people would definitely notice.

GlockandRoll · Post by **GlockandRoll** » Fri Sep 14, 2007 11:17 am

My USP tactical and SWR HEMS-2 is quiet... this is my friend Mark shooting, former APD.
http://www.youtube.com/watch?v=LgSkBCc8w2w

green0 · Post by **green0** » Fri Sep 14, 2007 5:30 pm

yeah WET.

Who cares? The magazine on my 1911 holds 8 rounds.

For all practical purposes, fire more than 8, and you don't need a silencer anymore because everyone would be aware of the bullets flying around.

It'll stay backyard quiet for sure through a magazine. Then it gets a little louder, for two more, and two more magazines and it's loud.

Everyone who needs more than a magazine on a charge or water/spit/or wire pulling gel, is generally shooting at a range where it doesn't matter anyway.

GlockandRoll · Post by **GlockandRoll** » Fri Sep 14, 2007 10:09 pm

I can shoot two 12 round mags through mine before it starts to pop a little.
It's still hearing safe dry, and I don't care what anyone says... I've got good hearing and I've heard mine dry w/out plugs.

supp-22 · Post by **supp-22** » Tue Sep 18, 2007 9:14 pm

What ammo are you guys using?

GlockandRoll · Post by **GlockandRoll** » Tue Sep 18, 2007 9:45 pm

I shoot Georgia Arms 230 JHP - good s--t!

Rgray · Post by **Rgray** » Tue Sep 18, 2007 9:52 pm

#93 wrote:I think you will be able to get a 45 can for an AR that will be hearing safe dry. The key to the 45 is having a lot of volume. That is much easier on a rifle than a pistol.

The DeLisle carbine, many Camp 45s, converted Spanish Destroyers and the Rihnland Arms conversions are all examples of 45 long guns with suppressors that work well dry.

2 years ago at the ISSMC I met a fellow who just got a 45 suppressed upper for his M16. I did not get to hear it but IIRC SRT did the work.

Your theory is what I am banking on. I have a KAC enroute that I will put on a Tactical and a UMP sbr. I know it is good on the USP cause I have shot one, but I dont know about the UMP 45 sbr.
Time will tell.

FALCON 1 · Post by **FALCON 1** » Wed Sep 19, 2007 8:15 pm

For any of you that are at the Suppressor Shoot on Sautrday check the Marlin 45acp Integral Carbine with a titanium tube at David Saylors Liberty Suppressor tent.

I asked him to build me a quiet 45acp and boy did he ever...........it may look like it is capable of shooting a .50 cal round but it digests 45acp like a 9mm or less.

Come by and shoot it.

FALCON 1

awdbandito · Post by **awdbandito** » Wed Sep 19, 2007 8:21 pm

FALCON 1 wrote: Come by and shoot it.

FALCON 1

I'll take you up on that offer. What ammo does it like? I'll pick up a box.

FALCON 1 · Post by **FALCON 1** » Wed Sep 19, 2007 9:22 pm

The Marlin likes 230 gr ball.

Stop by and ask for David Saylors or Derek Seltzer.

David is babysitting it until my NFA paperwork comes thru so I can only play with it for the day. Give him a Marlin 9mm which will be there as well or a 45acp carbine and he can do magic with them.

FALCON 1

awdbandito · Post by **awdbandito** » Thu Sep 20, 2007 5:50 am

I'm looking for an adequate .45 can for an AR I have. It isn't threaded yet, so it makes it hard for me to test a can. I look forward to giving it a shot or two.