Comment by bwhite | Hacker News Reader

Comment by bwhite | Hacker News Reader

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Sound suppression is largely a function of relatively slowly bleeding off the gas that results from combustion. There is not much powder in a 22lr (22 long-rifle) round, which is why it is easily suppressible. I can make no particular comment as to the frequency of their use by the best hit squads in the world.

The subject of the article was shot with a 22WMR (Winchester Magnum Rimfire) round. This round can use the same bullet as the 22lr round but contains lots more powder.

The velocity of the bullet leaving the barrel of the firearm depends on how fast the charge contained in the casing wants to push it and how much the barrel wants to slow it down due to friction. Almost all rifles barrels are between 16.5" and 24". For a average 22WMR round shooting an 40-grain (unit of mass) bullet out of a mid-length rifle barrel one would expect the bullet to leave the barrel at around 2000 feet/sec. The deceleration caused by friction can be altered by changing the exterior-most material of the bullet: a full metal jacket (usually lead totally encased by copper) is potentially slicker than a jacketed soft-point (only partially encased, with the tip exposed).

A Ruger Single Six is a type of handgun. The story describes a single-action revolver, which the Single Six is not, but let's ignore that. It comes in barrel lengths of 2.75", 4", and 6". Out of a 4" or 6" barrel, the 22WMR has about 1400-1600 feet/sec of velocity. This is roughly comparable with the upper (or hot) range for a 22lr fired out of a rifle barrel.

The story describes a single-action revolver, which the Single Six is not

The Single Six is, in fact a single-action revolver. See manufacturer's product page: http://www.ruger.com/products/newModelSingleSix/firearms.htm...

+1. My brain read Security Six. I think I suppressed a mediocre Single Six experience and foregrounded the delightfulness of the Security Six.

> There is not much powder in a 22lr (22 long-rifle) round, which is why it is easily suppressible.

Also, .22LR ammunition is generally subsonic outside of hotter loadings. This avoids the characteristic supersonic crack of higher velocity cartridges.

My gun shop sells .22LR ammo, and at a premium, a subsonic version (or at least, cartridges in boxes marked as such). Of all the .22LR ammo I've shot, none of it was marked subsonic and all claimed to provide supersonic muzzle velocities. Wikipedia seems to claims that 'regular' .22LR is supersonic (http://en.wikipedia.org/wiki/.22_Long_Rifle#Subsonic). Do you mean that most cartridges don't make their stated muzzle velocity and that in practice most .22LR is subsonic?

(as an aside, subsonic ammo is looked at suspiciously around these parts. since it's mostly used for poaching; when used with a home-made suppressor on a rifle, it's very quiet, like you say, in large part because of the lack of sonic boom).

Muzzle velocities are usually listed for rifle length barrels, sometimes absurdly long rifle length barrels to boost the numbers. 22lr out of a handgun length barrel will fall quite short.

Most manufacturers have quit playing those games. They generally (if you look) tell you what kind of weapon they were tested with, or barrel length failing that.

Doing a bit of googling, the .22LR doesn't gain much velocity beyond 14" barrel length, and loses less than 200fps from a 4" barrel vs the 14".

> and loses less than 200fps from a 4" barrel vs the 14".

Well, given that .22LR out of a rifle length barrel is less than 200FPS above subsonic speeds, that kind of plays right into what he was saying.

Yes that's true, I was thinking about rifles only, but indeed for handguns it would be different.

Sorry, but .22 Long Rifle is generally loaded supersonic from the test fixtures, even in the standard loadings. A pistol (assuming a 6" bbl) is really close to supersonic, if not a bit over. It'll vary by weapon and air density.

Now, you could use one of the other rimfire variations (.22 Short, .22 Long, .22 CB) which generally will fire from a .22 LR chamber. These would most likely get you subsonic velocities.

Another thing to consider when shooting a pistol vs a rifle and comparing sound signatures is that a pistol will eject more unburnt powder into the air around the muzzle as its had less barrel length to burn said powder.

As far as suppression goes, there are four main components of the sound signature of a gunshot:

1) muzzle blast - the expansion of deflagrating powder in the atmosphere as it exits the barrel.

2) sonic crack - the bullet creating a shockwave through the air. Can be avoided by using subsonic cartridges/loadings.

3) the weapons action - at the very least the firing pin's impact on the primer. This is louder than you'd expect.

4) the bullet's impact - very much louder than you'd expect. A rifle bullet impacting flesh is a very loud slap. Imagine dropping a large boneless beef roast on a tile floor from a few meters up.

Of these bits of the gunshot, only 1) can be addressed with a suppressor. And it does make shooting much more pleasant. You can generally avoid most ear protection shooting suppressed, even with supersonic ammo (you won't be in the shockwave so no need to worry about it).

I personally have fired rather large rifles without ear protection, and its generally not real pleasant. I really wish that there was no NFA and we could buy suppressors like some countries (New Zealand comes to mind). A .22 suppressor there is something like $40NZ, here you're looking at $4-600, a $200 tax stamp, and a 6month wait for the BATFE to do a background check that the FBI does in less than a week. Oh, and you can't let your wife/kid use it without being in violation of the NFA unless you have it owned by a trust where the family memebers are trustees.

I'm just going on chrono numbers I've seen in the past, e.g. http://www.hipointfirearmsforums.com/Forum/index.php?topic=3...

The only stuff that's consistently making supersonic out of the list is the high velocity stuff. Even Remington Golden Bullet (which Remington advertises as "high velocity" according to the box I have sitting on my desk) falls short of supersonic from pistol length barrels.

I guess the fairer thing to say would be that .22LR is borderline but it drops below supersonic pretty quickly once you start shaving barrel length.

As the saying goes, if OSHA were in charge suppressors would be mandatory.

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