Subsonic ammo?


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Sawdust
August 16, 2004, 01:58 PM
What does the term 'subsonic' mean when applied to ammo?

Thanks,

Sawdust

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foghornl
August 16, 2004, 02:01 PM
Bullet muzzle velocity is less than the nominal speed of sound, approx 1100 fet per second.

myopicmouse
August 16, 2004, 02:03 PM
It is slowed down so wont break the sound barrier - i.e you get no supersonic 'crack' also because of the reduced powder measue to make it travel slow enough it is quite quiet when using a sliencer. So the initial bang is reduced and you don't have that loud 'crack'

Sawdust
August 16, 2004, 02:30 PM
Thanks for the replies.

I'm hip to the speed of sound thing; by definition of subsonic.

I guess what I should have asked is "Why should I want to use subsonic ammo"? For example, is it because it's the best for use against hordes of mutant ninja zombies? Or, less stress on a gun for target practice? Etc.

Or...just "quieter"?

Sawdust

XLMiguel
August 16, 2004, 02:43 PM
It's just the nature of the round. The .45, at 850-900 fps, is a well proven stopper, as is the .357 magnum at 1350 and up. It's all part of the slow & heavy vs. light and fast argument, though in the final analysis, it all comes down to shot placement . . .:D

Hotter loads do require a stouter platform, however, and will likely cause more wear vs. 'target' loads. YMMV.

Mal H
August 16, 2004, 02:46 PM
There are several reasons to use subsonic ammo. One of the most important is that certain gun/ammo combinations aren't designed to use supersonic ammo. A good example is the 1911. If you push standard weight .45 ACP ammo to supersonic velocities, it will most likely exceed the stated pressure limits of both the gun and the casing. I'm quite sure that both the gun and the case will remain intact if you pushed the limits, but, again, it's not designed to do that.

Another reason to use subsonic ammo is demonstrated by the .2LR when used for high accuracy target shooting. It seems that if the bullet of a supersonic round goes subsonic before it reaches the target, a tiny shock is imparted to the bullet and affects accuracy. If you start off with a subsonic round, accuracy can be much better.

444
August 16, 2004, 02:52 PM
I think the main reason the fact that a certain load is specifically labeled as being subsonic is for use with a suppressor.
One of the big ones for that is the 9mm, 147 grain loads.
Obvioiusly in rifle ammo, the load has to be cranked way down to be subsonic at the muzzle. Often, with rifle suppressors, supersonic ammo is utilized and you do get a sonic boom. However, the boom doesn't occur at the location of the shooter. So, everyone knows a shot was fired but they just don't know where it came from.
Another area where this is often brought up is in extremly long range rifle shooting. Appearently (I am only repeating what I have read) when the bullet transitions from supersonic to subsonic this creates turbulance or something and greatly effects accuracy. So, you want the bullet to stay supersonic all the way to the target. This is a factor in 1000 yard rifle shooting as an example. Someone might ask about a certain load for use at 1000 yards and someone will respond that, that load will go subsonic before 1000 yards.

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