Subsonic 9mm ammo???

[alpha6164]

After 8weeks of weight time my tax stamp came in and i picked up my AAC Evo 9mm can for my Sig 226. I shot about a 100rnds of 115gr ammo and loved it. Although i am sure heavier slower bullets would sound even better. I know that speed of sound is about 1089ft/sec. Does that pretty much mean that i should look for ammo with velocity below this?

This pretty much leaves the 147 grain variety. I really like the Federal HST line and they have a regular and a +P 147gr. The standard pressure is advertised at 1000ft/sec and the +p is 1050 ft/sec. Am i correct to assume that both would be sound the same since they are below the sound barrier level and might as well go with the +p? All inputs appreciated.

Here are a couple of pics.

 

[KingTiger]

Nice set-up. Here's some Georgia Arms 147 gr. FMC subsonic at 950 FPS. They also make a hollow point round with the same specs. Alabama Ammo also makes "Special K" that is a similar loading.

 

[LiquidTension]

1050 fps is sort of the magic number for subsonic loads. Ammo is going to have a velocity range, some of it faster than others in the same batch. You get a slower round on a cold day and you run the risk of going supersonic.

I loaded some subsonic .223 that was running around 1080 fps. Took some out in the back yard in the neighborhood and was a little surprised when a sonic crack tore through the yard . It was about 30 degrees outside - forgot about that little detail hehe.

Temperature is the only thing that affects the speed of sound. At 68 degrees, speed of sound is 1126fps. At 30 degrees it's only 1085fps.

For serious work, you obviously want the fastest round you can get. If you're just plinking with your suppressed setup I would stick with standard rounds, especially if the +P costs more. There's really no need to squeeze an extra 50fps out of it. Any regular 9mm 147gr FMJ will work fine.

 

[19-3Ben]

KingTiger- jeeeeeebus that thing is quiet!!!

 

[Comanche180]

Speed of sound

Temperature is not the only variable in speed of sound. Density of the medium, which is affected by temperature is one thing. The density of air is also affected by the humidity. Humid air is lest dense than dry air.

 

[Gun Slinger]

Air pressure and altitude also have lot to do with the ambient speed of sound.

Although it does not take into account the variables for all of the factors that can influence the speed of sound, here is an equation that can give you a pretty close idea (within a couple of f.p.s.) of the speed of sound if you know what the air temperature (T) is:


√([273 + T] ÷ 273) x 1087.270341 f.p.s. = speed of sound


T is the air temperature expressed in degrees Kelvin which is obtained by adding 273 to the Centigrade temperature. (e.g.: 59.0F = 15.0C = 288K)

Regards,

 

[BlindJustice]

Spped of SOund

Commanche180 added Temperature is not the only variable in speed of sound. Density of the medium, which is affected by temperature is one thing. The density of air is also affected by the humidity. Humid air is lest dense than dry air.

It's also affected by altitude. - Ex-Sonar Tech.USN SPeed of SOund in Water is a little over 4X the Speede of Sound in AIr.

Randall

 

[BlindJustice]

I've been running various loads & bullet weights in a recently acquired
CZ 75B. It's been 100% reliable 115/124 & 145 gr. FMJ & JHPs.

Wally WOrld sells Win. 147 gr. JHPs
& I also ran a box of Win SXT 147 gr. JHP marked 995 fps
I like the way they shoot. I found one manufactuere who has a
147 gr. Hornady XTP JHPs @ 1,090 fps and it's a lot cheaper
than SXTs or SPeer Gold Dots so I'm going to order up several
boxes. Reeds Ammo & Research Okla City, OK. and it's not rated
+P

I did notice a quieter report from the sub-sonic loads at the
range the same day I shot 115 & 124 gr. loads.

Ron also offers a .38 SPecial 125 gr. Hornady XTP JHPs @ 1,000 fps
which shoot nice in my Model 60 J-Frame 3" Bbl. seems to have the same
abmount of recoil/muzzle blast as some SPeer 125 gr. +P GDs


Randall

 

[burningsquirrels]

kingtiger is that a gun or a cricket going off in that video?

 

[makarovnik]

Hollowpoint bullets traveling faster than the speed of sound expand more reliably in soft tissue than slower bullets. I not saying smaller faster bullet is better but you might want to consider this in your equation.

 

[BlindJustice]

Hollowpoint bullets traveling faster than the speed of sound expand more reliably in soft tissue than slower bullets. I not saying smaller faster bullet is better but you might want to consider this in your equation.

makarovnik


It really depends on what the manufactuere designed into the
particuliar bullet & weight - some designed for sub sonic might just blow up into bits - sigh, that's the problem with generalizations DUde, otherwise
.45 ACP hollowpoints wouldn't expand at all given your statement.

Randall

-

 

[Gun Slinger]

+1 BlindJustice.

Considering that the .45 A.C.P. launches a 230 gr. JHP at ~850 fps. on the "high side" and a 185 gr. JHP at 1025 fps., neither comes close to making 'transonic' (about 1050-1075 fps. depending on temperature) and would fail to expand.

Today's SD (handgun) JHP designs are more dependant upon "stagnation pressure" as a function of impact velocity to facilitate the mechanism of expansion and do not require supersonic impact velocities to ensure reliable expansion. Besides, the speed of sound in colloidal mediums (like human tissue) is four to five times that of the speed of sound in air and if this velocity 'threshold' were required to ensure relaible expansion in tissue, then even centerfire rifle rounds would be 'iffy'. Now that would suck!