sub sonic .22 ammo

[Tony Z]

.22 ammo is getting easier to obtain and LGS had quite a bit of it, along with quite of bit of what is labeled as "sub sonic". I've never shot any "sub-sonic", and my question is, beyond the obvious of being slower, what are other differences, if any?

 

[geetarman]

Most high end 22 ammunition is sub sonic. Many state that a 22 caliber bullet undergoes a wobble when transitioning from supersonic to sub sonic and my experience tells me the same thing. Slower is more accurate.

 

[98 220 swift]

I have for the most part found subsonic to be more accurate and in some cases much more accurate than the high velocity stuff. Actually the sub sonic is mostly what I buy and shoot anymore.

 

[JimPage]

As far as I know all bullets wobble while trans sonic.

 

[MarkCO]

"Standard Velocity" is typically 1050 to 1070 fps. There are a lot of terms that get used for various marketing and positioning. Better to just know what you are getting and for what purpose.

Here is a chart: http://www.ruger1022.com/docs/22lrballistics.htm

The speed of sound (Mach 1, transonic speed) is from about 1070 to 1170 fps depending on a lot of variables. I have found that I can shoot some ammo types to 1 MOA at say 90, 100, 110 yards, but beyond, it opens up significantly. The further out from the muzzle when a bullet goes transonic the worse due to loss of rotation (spin stability). The transonic does create disruption and destabilization for most rimfire ammo.

I tried a fast twist barrel to see if I could counter the stabilization issue and it does work, but the barrel fouls faster.

 

[carguychris]

The speed of sound (Mach 1, transonic speed) is from about 1070 to 1170 fps depending on a lot of variables.

Actually, there's only one variable that matters under most real-world circumstances: air temperature. Technically, the speed of sound varies with air density, and density is affected by barometric pressure and altitude as well, but these effects are so small that they can be disregarded most of the time. Basically, if you can survive outdoors without a space suit, temperature is the only thing that you need to be concerned with.

Here's a handy calculator, courtesy of your tax dollars:

http://www.srh.noaa.gov/epz/?n=wxcalc_speedofsound

FWIW according to the calculator, Mach I is 1,070 fps at 17°F and 1,170 fps at 110°F.

 

[MarkCO]

You are correct, T is the controlling factor. There are a lot of others, but their contribution is very small and can be ignored.

 

[Armorer-at-Law]

Technically, the speed of sound varies with air density, and density is affected by barometric pressure and altitude as well, but these effects are so small that they can be disregarded most of the time. Basically, if you can survive outdoors without a space suit, temperature is the only thing that you need to be concerned with.

What about humidity?

 

[carguychris]

...beyond the obvious of being slower, what are other differences, if any?

Some loads lack the recoil to operate the action of certain semi-auto firearms consistently, or at all. If you intend to shoot it in a semi-auto, buy a couple of small boxes for testing purposes before you stock up.

Some loads use heavier-than-standard 60gr bullets to maintain standard muzzle energy, most notable Aguila Sniper SubSonic or SSS. This may cause accuracy problems depending on the barrel twist rate. This is why special Ruger 10/22 barrels and Mk-series barreled receivers are sold for this load.

I have for the most part found subsonic to be more accurate and in some cases much more accurate than the high velocity stuff.

True, but to be fair, it should be noted that most high-grade target ammo is standard velocity and thus subsonic under most circumstances, and this ammo is made to higher quality-control standards than cheap high-velocity bulk pack. It's not an apples-to-apples comparison.

As far as I know all bullets wobble while trans sonic.

Correct, always. The reason is that a subsonic object pushes a shockwave in front of it, whereas a supersonic object compresses the air—essentially pushing it out of the way—and a shockwave forms at the rear of the object as the air returns to normal. At transonic speeds, the object is traveling through the shockwave (re: those awesome photos of fighter jets surrounded by vapor cones ); this has a destabilizing effect on bullets because no real-world bullet is perfectly concentric and flies perfectly straight, so the shockwave is always slightly asymmetrical with respect to the bullet's flight path, causing it to wobble. A high-precision match bullet fired from a match barrel can minimize this, but the effect is always there.

The reason more people are aware of this effect with reference to rimfire bullets is that most common rimfire loads go transonic at fairly short ranges by rifle standards, between 100yds and 200yds. FWIW some pistol calibers such as 9mm suffer from this issue as well, but most people never shoot these calibers at ranges over 50yds, so the issue is never noticed.

 

[geetarman]

This is a target I shot last week with my Anschutz rifle.

This was five shots at 50 yards.

Rifle is Anschutz MPR64
Scope is Vortex 6-24X ffp at 24 X
Ammo is Norma Match

This is the best 5 shot group I have ever shot in my life. This is quite a bit better than the factory test target provided with the rifle. The date is wrong. It was shot on the 23 of October.

 

[jag2]

Not sure what you are looking for info wise. You got a whole lot of tech, I didn't even try to understand it. Why I buy it (22 short sub sonic) is that it is very quiet and can be used (considering all safety issues) where you may not want anyone to know you are shooting. I even do a little target practice in the house. The LR subsonic is still quiet but the short is a lot better. Say I'm shooting squirrels in the back yard, the short is more than adequate.

 

[Erno86]

Subsonic 22 long rifle, definitely spooks the squirrels less.

 

[Tony Z]

Jag2 wins the prize! I want a quiet in-door type round.

 

[B.L.E.]

I shoot sub-sonic ammo both for its accuracy and for the absence of that whip-crack noise that supersonic ammo makes when it goes downrange. In addition to the trans-sonic instability, subsonic ammo experiences less wind drift than supersonic ammo does in .22 rimfire.

Five shots @ 50 yards. Winchester/Miroku 1885 Low Wall single shot rifle, Leupold 2-7X rimfire scope.

 

[carguychris]

...subsonic ammo experiences less wind drift than supersonic ammo does in .22 rimfire.

At a given range, subsonic ammo should experience MORE wind drift because the bullet is exposed to the wind for a longer period of time.

It should also experience a greater crosswind-induced gyroscopic precession effect, but most rimfire ammo is fired at ranges so short that the effect will be minimal, and most shooters are unlikely to ever notice.

 

[g.willikers]

Which ever ammo is used, wind drift has a definite effect.
Sometimes it's like shooting ping pong balls instead of bullets.

 

[Sharkbite]

I shoot A lot of subs out of both a bolt gun and a 10/22. I use them because those guns are suppressed 99% of the time. VERY quiet

The subs definitely hit softer then the high velocity stuff (as you'd expect), but the bullet performance on game is MUCH reduced. I try for head shots only when shooting subs.

I dont see a huge accuracy difference (group size) between like quality high velocity stuff and the subs ive shot.

Neither of my 22 rifles likes the Stingers much, although they shoot good out of my 22/45

I have found 22lr to be one of the most ammo sensitive calibers in my safe. Some ammo just shoots better then others. I have found the Gem-tech subs to be the most accurate sub ammo ive tried but as always YMMV. Believe it or not the 333rd Win white box bulk pack is the most accurate of the high velocity stuff ive tried.

Ive never shot any of the "match" ammo...too expensive and hard to find for me.

 

[B.L.E.]

At a given range, subsonic ammo should experience MORE wind drift because the bullet is exposed to the wind for a longer period of time.

Wind drift has nothing to do with time of flight, and everything to do with how much the air slows the bullet down during its flight.
Subsonic .22 long rifle retains a larger percentage of its muzzle velocity than high velocity ammo does.

A good way to understand wind drift is to change your perspective and define the air as stationary.

Now, instead of a stationary shooter shooting at a stationary target in a 15 mph cross wind, we have a shooter moving at 15 mph shooting at a target moving with him at 15 mph in a dead calm wind.

Let's put that target 100 yards away. The shooter is shooting across the deck of a big aircraft carrier that's 100 yards wide and steaming along at 15 mph in a dead calm wind. The motion of the ship makes the dead calm air feel like a 15 mph cross wind.
This air can't be drifting the bullet because it's a dead calm, all it can do is slow the bullet down.

So now the moving shooter is shooting at a moving target. The lateral motion of the shooter adds a 15 mph sideways component to the bullet's velocity that serves to give a built in lead that compensates for the moving target. Most aircraft gunners who have fired at ground targets are familiar with this phenomenon. You have to "lead" the ground targets just as if it was the ground that was moving and the plane that was stationary.

So, if the bullet kept its muzzle velocity all the way to the target, the built in lead from the shooters motion is just perfect to hit the moving target.

The more the air slows the bullet down, the later it arrives at the target and the more it hits behind the moving target.

Now let's look at a high velocity .22 long rifle load.
The muzzle velocity is 1260 fps.
The 100 yard velocity is 1023 fps or 81% of the muzzle velocity.
The actual time of flight is .258 seconds.
If the bullet had not slowed down during the flight, it would have covered 100 yards in .238 seconds. .258 seconds - .238 seconds = .02 seconds. The bullet arrived at the moving target .02 seconds too late due to the air slowing it down and that's enough time for the target to move 5.28 additional inches, resulting in a "wind drift" of 5.28 inches.

Now the standard velocity round, starting at 1080 fps and arriving at the target going 930 fps, 86% of its initial velocity. (remember, the high velocity bullet had slowed down to 81% of its initial velocity)
This bullet has a 100 yard time of flight of .290 seconds.
It should have gotten there in .278 seconds if it kept its 1080 fps muzzle velocity.

.290 seconds - .278 seconds = .012 seconds, the bullet got there .012 seconds "late" which gave the target time to move an additional 3.17 inches resulting in a "wind drift" of 3.17 inches

 

[laytonj1]

Wind drift has nothing to do with time of flight, and everything to do with how much the air slows the bullet down during its flight.

Wow. Not sure how aircraft carriers and moving targets fit into this but there is no magic rocket science involved.
All things being equal, the longer a bullet (time of flight) is exposed to a cross wind the more it will drift off course. It's that simple.

Jim

 

[B.L.E.]

Then why does a 1 ounce 12 gauge slug drift more than a sub sonic .22 LR? Is it because it's lighter?, no wait, 1 ounce = 437 grains.
Could it be because it slows down very rapidly?
Federal one oz slug
Muzzle velocity 1610 fps
25 yard velocity 1467fps 10 mph wind drift 0.3 inches.
50 yard velocity 1340fps 10 mph wind drift 1.6 inches.
75 yard velocity 1229fps 10 mph wind drift 3.7 inches.
100 yard velocity 1139fps 10 mph wind drift 6.6 inches.

These numbers came from Federal's website.

At 100 yards, it is still going faster than the standard velocity target .22 goes at the muzzle, therefore the time of flight has got to be less.

There's more to it than simple time of flight.

Whatever you say about my explanation of wind drift, my results very closely agree with the wind drift numbers given out by ballistic calculators.