subsonic 22

Frost

Active Member
wbond
the high road

http://www.thehighroad.org/archive/inde ... 81798.html



I'm a NOT a reloader, but I might have something to contribute that is worthwhile regarding accuracy and velocity.

There are other accuracy issues besides those I mention below, but what I say below is part of what makes or breaks accuracy.

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Bottom line: Keep your slower, heavier bullets 1050 fps or less muzzle velocity and your faster, lighter bullets above 1180 fps muzzle velocity, ideally above 1195 fps. Avoid all muzzle velocities between 1050 and 1180 fps, if you want good accuracy. Don't forget to take into account that the ammo maker probably used a longer test barrel. Alternatively, you can take the attitude the ammo manufacturer has, which is heck with it because handguns don't need to be that accurate.

I'll explain below.

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I have relatively little handgun experience, though I am not a novice. I have a lot of experience with .22 Magnum pellet guns (ya I said it), and with .22 Long Rifle and .22 Magnum firearms.

What in heck does that have to do with handgun accuracy? Everything because the velocities involved are similar and my pellet gun is a $400 RWS Diana that is more accurate than most .22 Long Rifles, at least to 65 yards.

Ballistics affect accuracy. Velocity affects accuracy. I'm not talking about bullet drop here, though it affects that too. I'm talking about the speed of sound and how the sound barrier affects accuracy in a negative manner.

Hi powered pellet guns and .22 long rifles have to be concerned with these issues because their velocities are near the sound barrier. The are either just below or above the speed of sound.

The sound barrier varies with temperature and elevation. Usually varies from 1080 to 1115 fps at common elevations and temperatures. For my purposes here I'm going to call the sound barrier 1100 fps because that's a common figure. When a projectile starts approaching the sound barrier the air starts bunching up in front of it and the turbulence increases right up to the point where the sound barrier is broken, which is the moment of violent turbulence (crack-bang).

When a projectile gets above approx 1050 it starts crowding the sound barrier a enough to cause turbulence that bumps the projectile off course a bit. It's like having a wobble in your steering. The closer the projectile gets to 1080-1100 fps the worse the turbulence, the more the accuracy deteriorates. That is why high-end pellet rifle manufacturers try to keep velocities below 1050 fps on most rifles, even if they have to use a heavier pellet to keep velocities down to 1050.

The turbulence starts to jostle the bullet and reduce accuracy the most above about 1060 or 1065.

The above was all in regard to object flying just below the speed of sound (heavier pellets from high powered pellet guns, heavier 40 grain bullets from .22 LR, and heavier slower pistol bullets. The heavier the bullet, the less the turbulence can affect it. i.e. - the greater the sectional density, the less turbulence matters.

For greatest accuracy, velocities must be kept below 1050.

However, to reduce bullet drop in rifles and to increase stopping power in rifles and pistols, a velocity increase is necessary. The question then is how to go super-sonic without losing to much accuracy? Simple, the greatest turbulence is just under the speed of sound (1060 to 1100) and just above speed of sound (1100 to 1120).

Just under the speed of sound the turbulence is bumping the front of the bullet. Just above the speed of sound the turbulence is bumping the rear of the bullet. At the speed of sound (commonly 1080 to 1100, sometimes up to 1115) the entire bullet is being bumped around by turbulence.

The trick to accuracy in a pellet rifle or .22 LR is either staying subsonic at 1050 or slower, or going super sonic and getting as far above the sound barrier as possible. i.e. - if you go fast enough you will break through the sound barrier so quickly and stay so far ahead of it that it doesn't have much time to affect your projectile.

What you want to avoid is staying close (just below or above) the sound barrer.

You especially want to avoid crossing the sound barrier twice (once during acceleration leaving barrel and again during deceleration downrange). Crossing the sound barrier twice means very bad accuracy.

By staying far enough below the sound barrier 1050 fps or less, you never get close enough to be affected much and never have to cross it.

If you want to go super-sonic for more energy or less bullet drop, then you need to get far enough above the sound barrier (1080 to 1100 commonly, sometimes up to 1115) that you cross it quickly and stay way above the speed of sound (way above 1115 fps) so your projectile doesn't catch turbulence from sound barrier.

Also, with super-sonic projectiles, you need to be far enough ahead of the sound barrier that you will stay above it down range. i.e. - you don't want the bullet to decelerate and get near or cross the sound barrier (a second time) before it hits the target.

For this reason, high-end pellet guns make a jump from 1050 fps with heavier pellets to 1250 with lighter pellets with no pellet weights-velocities in between. The idea is to either stay far enough below the sound barrier with a 1050 muzzle velocity, or stay way above it with a 1250 muzzle velocity with a lighter pellet.

Pellets have a very low sectional density and poor ballistic coefficient (not aerodynamic). So pellets decelerate much faster than pistol bullets. Pistol bullets decelerate much faster than rifle bullets.

The goal is to stay at least 30 fps below the sound barrier or at least 30 fps above the sound barrier at all times (even downrange). To stay at least 30 fps above at all times means that the downrange velocity must be at least 30 fps above the speed of sound (1115 + 30 = 1145 fps minimum acceptable downrange velocity at target).

For sub-sonic projectiles to stay below the sound barrier and still have decent killing power, the projectile must be heavy and large caliber. For super-sonic bullets to stay far enough above the sound barrier when downrange and have killing power, the bullet must be light or mid-weight and fast, which usually means a small to medium caliber. Only a magnum hand cannon can offer weight and high velocity, but the recoil is immense (like a .44 Mag). For manageable recoil you have to choose weight or speed. I like speed, but with as much weight as I can get and with 1150 to 1200 fps.

All this is very important to high power pellet guns that must hit targets 60 yds to 75 yds away. Also very important to .22 Long Rifle bullets. Because the .22 LR has a greater sectional density and a better ballistic coefficient (more streamlined), it is less affected by the sound barrier than a pellet. However, the .22 Long Rifle is used at longer ranges than a pellet gun. Often the .22 LR is used at 75 to 100 yds. So the affects of the sound barrier on accuracy over 75 to 100 yds are important. The .22 MAGNUM (firearm) rifle has a huge advantage over the .22 LR because the .22 MAG is way above the sound barrier both leaving the barrel (1800 to 2100 fps) and downrange at target. The speed of the .22 MAG is high enough to keep it far ahead of the sound barrier at all times, which is a big help at 100 to 125 yds both for bullet drop and accuracy.

How does this apply to handguns? The small caliber handguns I'm used to (.32 Mag and 9x18) lose about 50 fps over 25 yds. So the downrange velocity at 25 yds is 50 fps less than the muzzle velocity. This means muzzle velocity (if super sonic) needs to be high enough to keep the downrange velocity at least 30 fps above the sound barrier (1080 to 1115 with 1100 being most common).

i.e. - the minimum muzzle velocity of a super sonic handgun bullet should be 1100 + 30 + 50 = 1180 fps. Ideal muzzle velocity is 1195+. i.e. - 1195 fps or faster muzzle velocity is best for accuracy if dealing with super-sonic projectiles.

If the muzzle velocity is 1180 fps or faster, the bullet will usually be far enough ahead of the speed of sound to not be affected much by turbulence. i.e. - a supersonic bullet going 1180 fps or faster muzzle will be usually be accurate. However, higher elevations and/or higher temperatures can raise the speed of sound to 1115 fps (possibly higher). So to be really safe, the muzzle velocity should be 1200 fps or faster. The faster the better.

In other words, pellets and bullets with muzzle velocities of 1050 fps or less are the most accurate. 700 fps is the very most accurate muzzle velocity, which is why Olympic competition pellet guns have a muzzle velocity of 700 fps. However, good accuracy can be had up to 1050 fps muzzle velocity before needing to jump all the way up to 1200+ fps. That's why the most powerful hunting pellet rifles come in 1050 fps .22 caliber and 1250 fps .17 caliber versions. They don't make the .20 caliber mid caliber guns in the most powerful pellet rifles because the weight of the .20 caliber pellets would put their velocity right around the sound barrier. The .20 caliber pellet rifles are only offered in mid powered versions that don't have enough power to get near the sound barrier, but also don't have much hunting power.

Of the super-sonic bullets, as a general rule, the faster above the speed of sound you go, the better for accuracy. You need at least 1180+ fps muzzle velocity, but 1195+ fps muzzle velocity is best.

Muzzle velocities to avoid (if you care about accuracy): Avoid muzzle velocities between 1055 fps and 1180 fps. If you want to be a bit more liberal, then avoid those between 1060 and 1170 fps.

Also, you need velocity for stopping power. So if I were using a slower, heavier bullet; I'd try to get faster to be as close to 1050 fps as I could. Don't try to go faster than 1050, unless you can jump all the way to 1180+ fps.

If I wanted to use a faster, lighter bullet, I'd consider 1180 the bare minimum with 1195+ being ideal. The faster above 1180 fps the better the accuracy. However, bullets start fragmenting when velocities get to fast. How fast is to fast depends on your bullet, caliber, use, etc. However, I don't think you should have any fragmentation problems with good bullets from 1195 to 1300 fps.

That's why I prefer either a slower heavier bullet with 1050 fps muzzle velocity or a faster lighter bullet with 1195 to 1250 fps. I personally wouldn't go faster than 1250 fps muzzle velocity. I can also gain accuracy by having a heavier bullet with more sectional density and inertia. So in my opinion, if it's going over 1250 fps, I'd be looking for a heavier bullet to slow it down to 1250 fps muzzle velocity. Also, I think the bullet is less likely to fragment at 1200 to 1250 fps than at 1300+. That's why I think 1200 to 1250 fps is the ideal range of muzzle velocity, in my opinion. I realize that some cartridges can't do this. Many are to slow. Some are to fast. I think 1200 to 1250 fps muzzle velocity is ideal for the faster calibers. For heavier, slower calibers, 1050 fps is ideal. You don't have to agree, but that's my opinion.

If it's going under 1050, I'd be looking for a lighter, faster bullet to speed it up closer to 1050.

Of course, regarding bullet weights there are other issues such as caliber and sectional density that I won't go into further than to say that larger calibers offer greater sectional density, which helps accuracy.

To sum up: Slower and heavier bullets with 1050 fps muzzle or less are excellent for accuracy. Faster, lighter bullets going 1195+ fps are good for accuracy. I personally prefer the lighter faster option because I think it gives better stopping power, but that's just my opinion.

Slower, heavier bullets enjoy more sectional density and inertia which also help accuracy, plus they don't have to get near or cross the sound barrier. That's several advantages that make slower, heavier bullets more accurate, but I still prefer the ligher, faster option because that allows smaller calibers to have stopping power.

I personally prefer the heaviest, supersonic bullet that has from 1195 to 1250 fps muzzle velocity, if I can handle the recoil in that caliber. I consider 1225 fps muzzle velocity ideal. I like this combination because I think it's the best compromise of stopping power and accuracy I can get in a smaller (9mm) or mid-size (.40) caliber, plus bullets mushroom well between 1195 and 1250 and usually hold together too. This is one very good set of reasons why I like the .40 caliber S&W cartridge. However, I can't handle the recoil anymore (arthritis).

My next favorite is a 9mm Parabellum that has a velocity from 1195 to 1250 fps with whatever weight JHP gives that muzzle velocity. I think 1195 to 1250 fps gives the ideal combination of accuracy and stopping power with a recoil I can probably handle and bullets that mushroom and still hold together. 1225 fps muzzle velocity then should be ideal.

From purely an accuracy point of view, a subsonic 9mm would be best of the 9mms, but I've heard they have a poor history for stopping power, which makes sense because they lack the brute weight and diameter of a .45 and lack the shock effects of high velocity 9mms. Accuracy alone is not enough. Therefore the subsonic 9mm is not a good choice.

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I originally learned about accuracy and speed of sound from a pellet gun manufacturer.

I talked to an ammunition manufacturer about these issues and he said that he agrees these are important issues for pellet guns and .22 rifles. However, he thinks not very important for handguns since the combat range is usually 5-10 yds and a man is a big target. Therefore, handgun accuracy is not very important. Those are HIS words, not mine. He has a point from the typical combat point of view. However, I want all the accuracy I can get. I might want to shoot something at 25 yards or even farther some time, even if I am just plinking.

I'm not going to say which ammo manufacturer told me that because he's a nice guy and I don't want to embarrass him or his company.

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Speaking of cartridge manufacturers, they like to use longer test barrels then most people will ever use so they can inflate their muzzle velocity figures. Therefore, you need to figure out how much muzzle velocity your gun and barrel will give and use that for your muzzle velocity figure when shopping for ammo. I hope to buy a chronograph in the future. However, for right now, I have to use the estimate the ammo manufacturer gave me for my gun. He said that for a .32 Mag I can expect to lose approximately 33 fps per inch of barrel shorter than his 6" test gun. That's just an estimate. It's not really a straight line relationship, but his estimate is close enough for my gun. The best estimate for your gun will vary by caliber and other factors. If you don't own a chronograph, then you need to get a best estimate for your gun from a knowledgable reloader.

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Bottom line: Keep your slower, heavier bullets 1050 fps or less muzzle velocity and your faster, lighter bullets above 1180 fps muzzle velocity, ideally above 1195 fps. Avoid all muzzle velocities between 1050 and 1180 fps, if you want good accuracy. Don't forget to take into account that the ammo maker probably used a longer test barrel. Alternatively, you can take the attitude the ammo manufacturer has, which is heck with it because handguns don't need to be that accurate.

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What is the muzzle velocity and bullet type of the cartridge you are using? I suspect hollow points are more affected by sound barrier turbulence than a more sleek, streamlined bullet would be. However, JHPs are worth it. I also suspect boat tails are less affected by the turbulence of super-sonic flight. Super-sonic bullets have the greatest turbulence behind them because the sound barrier is behind them.

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I've read that some Finns pack vaseline into their hollow points to increase expansion and prevent the cavity from becoming clogged by clothing (such as denim). Supposedly, this works well for improving expansion. I wonder if it might help reduce wind drag or turbulence and increase accuracy? I'm considering trying this with melted beeswax, which would cool and harden. Perhaps the ammo manufacturers ought to do this with plastic? I know they do this for rifle ammo. Do they do it for pistol ammo?

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OK. Now I'm sure some of you guys are going to rip me up. Be careful this time because I can provide my sources for the speed of sound affecting accuracy of projectiles. I've been learning to expect a good b-slapping after opening my mouth. I'm ready this time. However, if you disagree, please keep it a friendly discussion with no personal attacks.

Thanks

















WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

Your comments are all exactly correct, but I'll bet that a human can't shoot a handgun accurately enough from a standing position to note the effects of the perturbation caused by the transition from super- to sub-sonic velocities.
I don't know what the target shooting distances are at the Olympics, but I think they are well under 25 yards for most competitions. They consider these things very important and try to have their target pellet rifles shoot 700 fps. i.e. - they think it matters under 25 yards.

Now I realize that the typical pistol shooter wouldn't notice the difference at 10 yards, but I think it would be noticeable at 25 yards. It would defineately be noticeable beyond 25 yards. I've personally experienced a substantial difference at 50 yards with a .22 rifle and also with my high-end German pellet gun. With the pellet gun, the velocity is adjusted by choosing pellet weight, which is how all the websites devoted to pellet guns say to adjust the velocity of a one cock gun.

Anyhow, I do think it would be noticeable with a pistol at 25 yards, but would anyone besides a target shooter care? Maybe not. I'm a decent shot, but my cousin is scary good. He just yesterday put 4 out of 6 shots through the same hole at 15 yards with my .32 Mag. He doesn't even practice. He can use all the accuracy my Ruger .32 Mag can give and he would likely notice any difference. I'm not good enough to know if it's me or the ammo, but a great shooter like my cousin can make use of all a gun and ammo have to offer.

I estimate my Ruger .32 Mag gives 1050 fps muzzle with the Federal 85 gr JHP ammo my cousin used. Federal says 1100 fps from a 5" barrel, but my barrel is only 3". I'll know as soon as my Shooting Chrony arrives. I also read that the Federal target ammo for .32 Mag is heavier (95 gr) and slower at well below the sound barrier. I think Federal wants their target ammo sub sonic for a reason.

Anyhow, I think it does matter at 25 yards and farther for pistols. I think it might matter at 15 yards. That is my opinion.
 
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