What causes the louder sound in factory 115gr?

[98006]

I shoot mostly 147gr reloads. Every time I shoot factory 115 gr ammo, I realize how much louder and more blast they have compared to my reloads.

So whats the cause of it? the powder used?

[lcs]

I shoot mostly 147gr reloads. Every time I shoot factory 115 gr ammo, I realize how much louder and more blast they have compared to my reloads.

So whats the cause of it? the powder used?

A lighter bullet has to be pushed faster. More powder=louder (most of the time) and yes some powders are louder than others.

[carharttfarmer]

your 147s are subsonic and factory 115s are super sonic= more noise

[usmc1974]

your 147s are subsonic and factory 115s are super sonic= more noise

yep, sound barrier

[CocoBolo]

I'm going with sound barrier because the speed of sound at 68 degrees F is 1,126 fps. Most factory ammo of the 124/5gr variety is about 1040 fps however Win White box 115gr is rated at 1155 fps. 147gr are typiically less than 1000 fps.

Additional powder also plays a part as well as the specific powder. Hogdon has one called Loud Shot, oooops I meant Long Shot, it is louder than other typical powders.

[lugnut]

Maybe subsonic has some do do with it... but 40 and 45 rounds seem damn loud to and they are often super sonic. I think the lighter bullets tend to have powder still burning as the lighter bullet exits the barrel Heavy bullets with faster powder usually is all burned off by the time the bullet leaves. Slow powder has a large effect on sounds... just load up some Power Pistol loads and compare them to N320 for example...

[mizer67]

Hogdon has one called Loud Shot, oooops I meant Long Shot, it is louder than other typical powders.

So's Alliant's Power Pistol.

[Tom E]

Has to do with loadings that have more pressure in the barrel when the bullet exits. Less time in the barrel with lighter bullets means making pressure longer if max pressure is limited by standards. It's a time/pressure function. Same reason open guns are so loud (and why their ports work), pressure in the barrel as the bullet clears the port(s).

Edited July 23, 2011 by Tom E

[freakshow10mm]

When the bullet is in supersonic flight, what's happening is the velocity is so fast that it creates a V of airflow around the bullet. Behind the base of the bullet has no turbulence. This area is where a vacuum exists. The sound you hear as a supersonic crack is the air on both sides of the bullet rushing it to fill that vacuum (high pressure to low pressure) and it makes the sound.

[Nealio]

So's Alliant's Power Pistol.

When I was running 100gr bullets @ 1350 I would be asked if I was shooting .38 Super or 9mm major at almost every match I went too...

Edited August 3, 2011 by Nealio

[Dmonwai]

I'm going with sound barrier because the speed of sound at 68 degrees F is 1,126 fps. Most factory ammo of the 124/5gr variety is about 1040 fps however Win White box 115gr is rated at 1155 fps. 147gr are typiically less than 1000 fps.

Hmm, that explains why in a lot of the matches I shoot others in my squad say my rounds are so loud... I shoot Win White box 115gr a lot and have had many times when others in my squad ask what what I'm shooting because they say its so loud. They are surprised when I say its just Win White box 9mm.