I have a Schmidt Rubin K31 that uses 7.5x55 (GP 11) ammo and it travels at 2560 fps with a psi of 45,000. It’s a 26 3/8 inch length barrel from the end of the bolt when in the firing position.
At what point in the barrel does the bullet go into hypersonic?
It doesn’t. 2560fps is only a bit above Mach 2. Typical hypersonic speeds are Mach numbers greater than 5.
:smack:
Thanks.
What if he was running backwards while firing, wouldn’t the realative speed then be… :dubious:
Why is there no sonic boom?
There is. It’s usually masked by the sound of the discharge.
I believe the part of the ‘crack’ you hear when a rifle goes off IS the sonic boom, but i may be wrong.
My question is: what is hypersonic?
I was under the impression that anything higher than the speed of sound would be supersonic and that Mach 1 was the speed of sound…and that the actual M.P.H. speed of Mach 1 varies depending on atmospheric pressure and altitude (?)
I’ve never heard the sound hypersonic and assume that it’s something different than supersonic.
Cool…Thanks.
I never knew that.
Here are a couple of videos that might interest you, Reeder.
http://www.swrmfg.com/video/omega1.asp
The video on the left is a suppressed rifle firing conventional .30 caliber supersonic ammunition. You can plainly hear the crack of the bullet’s supersonic flight.
The video on the right is the same rifle firing subsonic ammunition. Much quieter, no crack. Very cool.
Hypersonic: Of, relating to, or capable of speed equal to or exceeding five times the speed of sound.
Sweet videos Berkut.
Thanks…!
Another question.
What is the purpose for supersonic ammunition?
Most ammunition is supersonic by default. A higher velocity means a flatter trajectory and more energy delivered to the target, everything else being equal.
Flat trajectory I understand.
But isn’t a bullet hitting a target at a speed so fast it’s going to go straight through without hanging around a bit to do a bit more damage sort of defeating the point?
It depends on what you’re trying to accomplish.
If you are hunting large and dangerous game, you might want a very sturdy bullet that doesn’t expand much when it hits your target. Higher velocity here means more penetration to reach vital organs in a tough animal.
If you are looking to do a lot of damage by using an expanding bullet, the higher velocity on impact will usually mean more expansion and more damage done. For a small animal like a groundhog, you want almost explosive expansion. Here are some pretty good videos showing the damage a high velocity rapidly expanding bullet can do.
When it comes to firearms, higher velocity is almost always your friend.
They don’t usually just travel straight through the target if you are talking about a human or an animal. Most bullets are designed to mushroom when they hit the target. This causes a much bigger hole than if the bullet stayed in its original shape and the mushroomed bullet sends a massive shock wave through the body, causing substantial organ damage.
Very fast bullets give you a longer range. Remember that a bullet fired straight will hit the ground at about the same as a bullet dropped from the same height. The further the bullet goes in that time, the longer the range. It also makes it much more easy to aim if the bullet is at roughly the same height at 100+ yards as it was out of the barrel. Rifles used for hunting, war, or long distance target shooting need that extra speed to be effective.
Bullet construction varies with velocity and type of game. A .22 caliber .45 grain bullet for hornet ammunition may have a thin copper jacket so it expands at the modest velocities of that round when it hits a ground squirrel. The bullet is so fragile relative to other bullets that using it in a higher velocity cartridge can cause it to disintegrate just from the forces of spinning through the air. A bullet for heavy african game will have sturdier construction, sometimes with no lead core at all so they don’t disspate energy before penetrating deep.
Nope, not nearly that clear cut. We’ve done this before so I’ll just copy my comment from there.
This is not a hard and fast rule. There is no clear cut boundary between supersonic and hypersonic. Hypersonic is defined as a flow in which certain effects become more significant than they are at lower supersonic speeds. These effects include very thin shock layers (shock waves close to the body), relatively thick boundary layers because high temperatures increase viscous effects, chemically reacting boundary layers (because of high temperature), very low density where you might even get temperature and velocity slip at the surface and some other effects I don’t recall at the moment.
There’s a relatively famous (at least within the field) quote from some old smart guy pointing out that most people agree that hypersonic flow starts at Mach number 5 or 6, but it’s possible to make the argument for a boundary as low as 3 or as high as 12. The point is, the change from supersonic to hypersonic is not a clear boundary like subsonic to supersonic. It’s a gradual change where some effects that are negligible at lower speed become more important.
While I agree that there is no definite rule for where the boundary is (and I’ve heard the arguments for 3 and 12), I’ve never heard Mach 5 seriously disputed as a rule of thumb until one begins to discuss the aerodynamic effects. Just as we say “93 million miles” for the distance from the sun to the earth even though our orbit isn’t perfectly circular, “Mach 5” is as good a rule of thumb as any.
Oh man. Now I feel obligated to argue with the Master, as “hydrostatic shock” is, in fact, technobabble rather than real science. Too tired. Do it another time. At this time I’ll leave it that on many amateur gun web sites you will find “hydrostatic shock” referenced. But if you read FBI and military reports that show actual experiments, this supposed effect is debunked.