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Why can’t I go supersonic?

by B.B. Pelletier

Why can’t I shoot pellets faster than the speed of sound? There’s a question that pops up all the time, so I thought we’d take a look at it today.

For starters, read the Velocity and pellets article. It addresses all the problems with supersonic velocities and diabolo pellets. But that article still doesn’t answer the question everyone asks, “If airgun makers are building guns that shoot supersonic, don’t they mean for them to be used that way? Maybe, but maybe not.

Don’t imagine that airgun makers run exhaustive tests to find out everything their guns can or will do. Nobody does that. They are concerned with operation and safety. Does the gun work and is it safe? If not, it’s back to the drawing board. The gun should also be accurate, although accuracy depends on the intended use for the gun. A target gun has to be very accurate at 10 meters, but nobody cares what it does at 50 yards. A sporter has to be accurate at longer ranges, but don’t expect 10-meter target accuracy. You may get it, but don’t expect it every time.

Okay, what does all this have to do with supersonic velocities? Nothing! Supersonic velocities come into play in another way – advertising.

A lot of cars are sold on the basis of the lifestyle they represent. Firearms are sold that way, too. A hunter in Ohio may buy a .375 H&H Magnum rifle even though he never intends to use it on game. A .375 H&H in Ohio is about the equivalent of a Ferrari Testarossa in an Akron garage. It’s braggin’ rights, pure and simple.

Back to airguns. Manufacturers know that today’s buyers are obsessed with velocity, so they advertise their guns that way. In the past, it was normal for certain Chinese air rifles, like the B3-1, to be advertised as shooting 800 f.p.s., when the best B3 actually had difficulty hitting 500 f.p.s. Other airgun models from England and Germany fudged their advertised velocities a little, though none were as blatant as the Chinese.

Then chronographs became affordable and people began to discover the truth for themselves. About the same time, companies like Beeman and manufacturers like Diana were publishing credible velocities for their guns. So, in the late 1970s the world of airgunning switched over to truth in advertising, for the most part. But in 1983, the new Beeman R1 broke 1,000 f.p.s. honestly for the first time. In the mid-1980s, Diana followed suit with the sidelever model 48/52, which exceeded 1,100 f.p.s. (all of this is in .177 caliber).

Then in the mid-1990s, the Koreans came here with powerful rifles, such as the Career 707, which could shoot .22-caliber pellets at speeds in excess of 1,200 f.p.s. The race for high velocity was on! Unfortunately, nobody was asking whether these guns were accurate at those speeds.

As it turned out, the guns were accurate, but with pellets that were so heavy they slowed muzzle velocities down to subsonic levels. However, that wasn’t what people wanted to hear, so the report went out like this, “A Career 707 is very accurate at long range and it will shoot a .22-caliber Crosman Premier in excess of 1,200 f.p.s.” Yes to the first statement and also to the second, BUT NOT TOGETHER!

Now, here’s the real crusher. It may be that a super-powerful rifle will shoot a certain pellet faster than sound and also be reasonably accurate at 50 yards! How can this be? Well, not every group will be accurate, but you may get one out of five that looks great. So the owner of that rifle posts that one group on one of the chat forums and talks about it as though he always gets groups that good. In truth, he might be able to shoot much more accurately with a heavier pellet, but the muzzle velocity will not be as impressive. So, that’s his story and he’s sticking to it!

High velocity with diabolo pellets is an advertising strategy. And it works. If you own an airgun capable of high velocity, try shooting it with heavier pellets and see what happens to your groups at long range. Some of the best heavyweight pellets on the market are Beeman Kodiak (also sold as H&N Baracuda), Eun Jin/Sumatra, and Pyramyd Air’s own Predator pellets. Kodiaks are 21 grains and will work well in almost every powerful air rifle. They come in .177, .20, .22 and .25 calibers. The Eun Jin pellet comes in all calibers, but they should be used in rifles capable of over 40 ft.-lbs. of muzzle energy. Predator pellets come in .177, .22 and .25 calibers and several different weights. They are solid bullets rather than diabolo pellets, so exercise the same caution when shooting them as when shooting a .22 rimfire rifle. They can carry over one mile, just like the bullet from a .22 short cartridge. They are harder to load because they are solid, so expect some resistance when they enter the bore.

So, supersonic velocities are possible. Accurate guns are possible. But not necessarily together.

9 thoughts on “Why can’t I go supersonic?”

  1. Firearms are accurate at supersonic velocities because their bullets are streamlined for supersonic flight. And some firearms have problems, too. The .22 long rifle, for instance, has a velocity so close to the sound barrier that target ammo is purposely made subsonic so it won’t have the problems mentioned in this blog.

    The most inaccurate .22 long rifle rounds are the new hypersonic rounds that go 1400 to 1600 f.p.s. They shoot all over the place.


  2. BB,
    Given that these Predator ‘pellets’ (or bullets) already exist, I dont understand the buzz abt piledrivers right now. Looks like more or less the same deal to me. Except the boat tail on the PD.

  3. majorkonig,

    The buzz is being created by a company that distributes Piledrivers in the UK. They are trying to promote the product, and much of what you see on chat forums is them or their agents coming in from European URLs.

    When American shooters test the Piledriver, they get different results than the buzz whould lead you to expect. Surprise!


  4. It has been my experience that supersonic pellets are usually accurate at very close ranges(20 ft) and then start flying wild. A 30 ft group may be over twice the size of the 20 ft group. My theory is that diablo pellets do not have a good cross sectional density and lose energy to wind resistance very quickly. When the pellet drops to subsonic, the supersonic shockwave catches up and bumps the pellet.

    If you are performing pest control at very close ranges, the hydrostatic shock caused by a supersonic pellet causes much more damage than a heavy with lower velocity, usually with cleaner more humane kills as a result.

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