Awesome shock wave pics: .44 and .30-06

[JesseL]

What if you modify a MAC-11 .380 to be even faster? Lighter bolt or something.

Even with a cyclic rate of 2000 rounds per minute and a ridiculously low velocity of 500 fps the bullets would be coming out 15 feet apart (assuming I haven't really screwed up my calculations).

 

[chris in va]

Those of you that haven't clicked on the link yet, here's how it's done.

And for those of you asking about other guns, here's a 22 target pistol and AK 47.

 

[MinnMooney]

Great pictures!

+1 on the muzzle brake pic if you can get one.

I looked (googled) and couldn't find one using a muzzle brake.

 

[230RN]

I wonder if one of those magnifying makeup mirrors would be suitable. Anyone know the focal length on one of those?

 

[La Pistoletta]

Even with a cyclic rate of 2000 rounds per minute and a ridiculously low velocity of 500 fps the bullets would be coming out 15 feet apart (assuming I haven't really screwed up my calculations).

Then I guess they should borrow an M134.

 

[JesseL]

Then I guess they should borrow an M134.

Nope, even at 6000 rounds per minute the velocity of the 7.62 NATO round (around 2750 feet per second) puts the distance between individual bullets at 27.5 feet.

 

[atblis]

Those are FAKE!

 

[Huddog]

I wish I understood the science more. Why is the .44mag shockwave larger than the 06 one. I would have expected it to be the other way.

 

[La Pistoletta]

Nope, even at 6000 rounds per minute the velocity of the 7.62 NATO round (around 2750 feet per second) puts the distance between individual bullets at 27.5 feet.

MetalStorm then. Happy?

 

[scrat]

those pics are sooo coool

 

[CypherNinja]

I wish I understood the science more. Why is the .44mag shockwave larger than the 06 one. I would have expected it to be the other way.

Timing. They simply caught the shockwaves at different times. The camera clicked slightly later for the .44 than the .30-06.

 

[wally]

File this away for next time folks argue about "gun recoiling while the bullet is moving down the barrel".

Note how far the bullet is down range with virtually no visible effect from recoil, yet!

--wally.

 

[La Pistoletta]

Note how far the bullet is down range with virtually no visible effect from recoil, yet!

That's because they don't make guns as light as bullets. I bet if you ignited a cartidge laying on the ground, with the casing acting as the "gun", the case would fly backward pretty fast.

 

[wally]

Paraquoting Hatcher:

"Manufacturers take this pre-exit recoil into account when they design fixed sight revolvers whether they realize it or not. If you draw a line from the sight and another line from the axis of the barrel, you will see that the sight line points upward from the bore axis to take this pre-exit muzzle flip into account."

That's right, because revolvers have two recoils -- at the barrel cylinder gab and the muzzle, rifles and pistols have on the one at the muzzle. The first recoil will affect the POI.

American Scientist is very reputable and basically read by professional nit-pickers . I regret not staying subscribed to it but the Sigma Xi membership dues got pretty high at a time I was broke from a divorce. Maybe I should look at joining again, I loved that magazine, but other than that, I'm not a go to meetings kind of guy to get much from the organization.

--wally.

 

[wally]

That's because they don't make guns as light as bullets. I bet if you ignited a cartidge laying on the ground, with the casing acting as the "gun", the case would fly backward pretty fast.

True enough, but its irrelavant to my pointing out the POA/POI shifts with different bullet weights are dominated by "barrel harmonics" not recoil -- changes in the race between the bullet and the transverse & longitudinal pressure wave displacement of the muzzle at the bullet's exit is the dominant cause of the different POI.

--wally.

 

[1911Tuner]

File this away for next time folks argue about "gun recoiling while the bullet is moving down the barrel".

Physics 101.

"For every action, there must be an equal and opposite reaction."

What part of "equal" is so hard to grasp?

Reaction begins at the instant that action begins. You can't have force applied in one direction, and you especially can't have force in one direction...and then a second force applied in the other direction later on...within the same system during the same event.

Can't happen, Kemosabe.

Go push on a table. You're immediately pushed BY the table via the force vector provided by your tricep.

Pull on a table. You're immediately pulled by the table via the force vector provided by your bicep.

There is no delay. Action and reaction start at the same instant.

During a ballistic event, a vectored force acts on the base of the bullet and the bolt/breechblock...through the case head...driving both in opposite directions. Force forward equals force backward. The same level of force imposed on the bullet is imposed on the bolt. These forces are imposed at the same instant.

The bullet moves faster because it's less massive than the rifle...and don't forget the shooter's mass in resisting movement. It's figured in, too.

The momentum of the bullet and the momentum of the rifle are also equal...even though one is moving slower. Momentum is Mass X Velocity.

See? Equal.

"For every action, there MUST be an EQUAL and opposite reaction."

So...Yes Virginia. Recoil is in full swing before the bullet leaves the barrel.

 

[Captal_de_Buch]

Now I know why I always end up with a headache when I put 100 round through my Ruger RedHawk 44mag.

 

[1911Tuner]

That's right, because revolvers have two recoils -- at the barrel cylinder gab and the muzzle, rifles and pistols have on the one at the muzzle. The first recoil will affect the POI.

No...There's only one. Whatever the residual gas jet effect in a pistol after bullet exit wouldn't amount to enough to knock a fly off the gun.

The mass of the gasses and residue is equal to the mass of the unburned powder, minus the oxygen consumed. Momentum is Mass X Velocity. Since the velocity of the gasses can't be higher than the bullet at exit...a 6 grain powder charge at 1,000 fps would generate a recoil impetus roughly equal to a CB cap.

 

[1911Tuner]

True enough, but its irrelavant to my pointing out the POA/POI shifts with different bullet weights are dominated by "barrel harmonics" not recoil

If you've got a .357 Magnum revolver, you can do a little test to see how much recoil affects point of impact.

Use identical ammunition for both tests.

Fire a group with sandbags under your wrists with a firm, two-hand grip.

Then...using the same sight picture and point of aim...place the butt of the gun on the bags, and steady it by encircling the bottom of the grip with your thumb and forefinger. Use the thumb and finger of the strong hand to "pinch" fire the gun...so as not to disturb the sights, and compare the placement of the second group to the first.

Now...It won't change because of barrel harmonics or vibration or other such nonsense. It'll be due to the gun rolling upward on the pivot point at the butt and the sand bag as opposed to not rolling upward when the pivot point is lower as when fired normally.

Barrel harmonics is a rifle thing. Pistol barrels are too short and rigid for it to make any practical difference.

Just in case you never used it...

Pinch firing entails using the thumb agains the back of the trigger guard and the tip of the finger n the trigger. It's a very neat way to fire a gun without jerking the trigger. Works well with bolt-action rifles for precise shots.

 

[brickeyee]

The mass of the gasses and residue is equal to the mass of the unburned powder, minus the oxygen consumed. Momentum is Mass X Velocity. Since the velocity of the gasses can't be higher than the bullet at exit...a 6 grain powder charge at 1,000 fps would generate a recoil impetus roughly equal to a CB cap.

Problem here.
The mass of the burned powder is equal to the mass of the unburned powder.
Powder contains both fuel & oxidizer.
It is not dependent on atmospheric oxygen.
The hot gases will react with atmospheric oxygen once they are out of the barrel though.

The gases can have a higher velocity than the bullet.
As soon as the bullet clears the barrel they are unconfined.
Look at the various high speed pictures.
The bullet can be seen lagging behind the gases until they slow down.
Having a very low mass they have no momentum to maintain speed.

For handgun cartridges the powder mass is usually small compared to the bullet mass.
For rifles the powder mass can be a significant fraction of the bullet weight.

 

[1911Tuner]

Powder contains both fuel & oxidizer.

...and the oxygen released is consumed during burning. Agreed?
(We ain't talkin' a huge difference here.)

The gases can have a higher velocity than the bullet.
As soon as the bullet clears the barrel they are unconfined

Now we have a disagreement.

Mass requires force to accelerate it to a given velocity. The velocity of the gas can't be higher than that of the bullet while the bullet is blocking its path of escape.

Once it's unconfined, the mass of the gas can't accelerate to a higher velocity unless a new force is introduced any more than a bullet can accelerate to a higher velocity after leaving the barrel simply because it's free from the barrel's frictional resistance. No?

No. Once the bullet or the gas is free from compulsive AND resistive force, they then comes under new forces that are working to slow them down. Namely...air and gravity. Without a new force to overcome that resistance...all they can do is slow down.

 

[PercyShelley]

Gas escape velocity will depend upon barrel length. The longer the barrel, the more volume they will fill and cool adiabatically and convectively. Lower temperature means lower velocity.

On a very long barreled .22, for example, I would expect that the bullet would be going substantially faster than the exhaust gas' effective velocity. Ditto a ported-barrel style suppressed gun like an MP5SD.

 

[ojh]

Watch the high-speed video of a firing 1911 at http://www.kurzzeit.de/startseite.htm . You can clearly see two things:
1) Slide & barrel are moving backward before the bullet comes out of the barrel => recoil starts when the bullet is still in the barrel. Hatcher has is right.
2) Just when the bullet clears the barrel, a puff of gas rushes out faster than the escaping bullet.

 

[1911Tuner]

Just when the bullet clears the barrel, a puff of gas rushes out faster than the escaping bullet.

What you have just at the point of bullet exit...for a brief fraction of an instant...is a restriction around the bullet base created by a narrow gap between the muzzle crown and the bullet. This may accelerate the residual gasses that are still under pressure a little faster than the bullet...but not much and not for long...and the volume of the gasses is a small portion of the total. The pressures too, are lower than peak by a good bit. Depending on the powder burn rate/area under the curve and the mass of the gas plug...the pressure can be as little as 10-12% of peak.

Bottlenecked rifle cases offer a completely different set of dynamics. Neck and shoulder create a venturi effect, accelerating the gasses...and depending on the volume of that gas...can continue to generate a detectable recoil impetus on the breechblock after the bullet is gone...however briefly.

Large volume/small caliber rifle cases offer the most "aftershock" because in some...the powder charge weighs nearly as much as the bullet, and the venturi effect is greater due to the neck diameter.
The .220 Swift is one such. The .22-250 is another example.

Straight-walled pistol cases with small powder to bullet mass ratios?
Wouldn't dislodge an eyelash...

 

[benEzra]

File this away for next time folks argue about "gun recoiling while the bullet is moving down the barrel".

Note how far the bullet is down range with virtually no visible effect from recoil, yet!

But ALL the effect from recoil that affects the trajectory of the bullet HAS happened by the time the bullet leaves the barrel.

It's not the amount the rifle moves that affects the bullet's trajectory; it's the velocity component of that movement that alters the bullet's vector ever so slightly. And the rifle is moving at near its full rotational and linear recoil velocities by the time the bullet reaches the barrel.

BTW, 6 inches difference at 100 yards is only 1/10th of a degree of muzzle rise. Can you see 1/10th of a degree of muzzle rise from a photo that small? I can't.

True enough, but its irrelavant to my pointing out the POA/POI shifts with different bullet weights are dominated by "barrel harmonics" not recoil -- changes in the race between the bullet and the transverse & longitudinal pressure wave displacement of the muzzle at the bullet's exit is the dominant cause of the different POI.

You can induce different points of impact with the same load by holding the forend down very tightly for one string and then by letting the forend rise freely (much looser hold) on the next string. That's recoil, rather than barrel harmonics.