Another Slo-Mo Video - 4 Calibers, Side by Side

[etrain16]

No doubt you've all see the Slow-Mo guys on YT. They just posted a new video where they compare bullet speeds from 4 different guns, side by side. They use a 9mm, .45acp, 7.62x39 and .416 Barrett

The side-by-side comparison of bullet speeds is very interesting to watch and starts about 3:30. I think we all know which would be the fastest, but when you see them next to each other, you really get a feel for how much slower a pistol round is, especially the .45acp

Something else interesting comes in at about 2:25 - on the AK they were using for the 7.62x39, you could see something I don't recall seeing before - the barrel flexing, quite a bit, as the bullet exits. I don't know if that's normal for an AK, but it was an eye opener for sure.

Under 7 min video, definitely worth the watch.

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[Levetti]

Yes, the barrel flexing on an AK is normal.

 

[Boboclown]

Something else interesting comes in at about 2:25 - on the AK they were using for the 7.62x39, you could see something I don't recall seeing before - the barrel flexing, quite a bit, as the bullet exits. I don't know if that's normal for an AK, but it was an eye opener for sure.

It is normal. Any rifle will have its barrel flex when being shot, this is why free floating handguards exist. You don't see this happen because it all happens very fast.

Shorter barrels tend to be more accurate than longer barrel, at least in theory, due to them being more rigid and have less flex. Same with heavy barrels.

 

[HB of CJ]

Regarding the barrel flex. Could, (could) it be lensing effect from the air pressure compression waves? I wonder if some gages were placed on the barrel would they record such visual barrel flexing. I may be dead wrong but it seems unlikely, (to me) that such a rigid barrel could bend so much.

How much energy is there propelling that bullet to that muzzle velocity? Compare that to the energy required to instantly flex the barrel out of axis to the bullet track. The two potentials do not add up in my feeble minds eye. Thus there must be something else going on. That might be lensing?

Just me.

 

[Boboclown]

Regarding the barrel flex. Could, (could) it be lensing effect from the air pressure compression waves? I wonder if some gages were placed on the barrel would they record such visual barrel flexing. I may be dead wrong but it seems unlikely, (to me) that such a rigid barrel could bend so much.

How much energy is there propelling that bullet to that muzzle velocity? Compare that to the energy required to instantly flex the barrel out of axis to the bullet track. The two potentials do not add up in my feeble minds eye. Thus there must be something else going on. That might be lensing?

Just me.

Its from the force of the bullet speeding through the barrel. YOU may have a hard time bending it. The bullet flying at 2350 feet per second, however, will not.

This is why free floating barrels exist, so the barrel harmonics are not affected by attaching anything to the handguard.

 

[Boboclown]

Its also not just the barrel that will flex, the entire rifle will flex. Some more than others, but you won't notice it because it happens too fast for you to see it. The only way you will notice is if you watch a slow motion video.

If you want to appreciate the stuff your optics go through:

 

[HB of CJ]

Respectfully.

I still believe it to be an optical illusion. How could a scope possibly be flexed THAT MUCH THAT FAST and be expected to live? Again, the energy required to accelerate a bullet vs the energy required to instantly flex the barrel and scope. I still think somebody should do the test using actual gages on the barrel. Again just me. The test would be fun.

Respectfully.

 

[Boboclown]

Sounds like you're joking at this point.

 

[HB of CJ]

No.

 

[Boboclown]

For every action there is a reaction. The amount of force required to push the bullet that fast is also going back into the receiver, this in addition to it being semiautomatic, is going cause the gun to flex. As for the barrel, the bullet flying that fast (and spinning at the same time mind you) is going to cause the barrel to flex. This happens very fast, this is why its important that guns are made to within a certain spec. They can't be too rigid, and they can't be too weak. This is all normal.

Its why free floating handguards exists, its so attaching something to the handguard does not change the way the barrel flexes, as a result it won't change the point of impact.

 

[HB of CJ]

Now thinking about HOW such an interesting experiment could be conducted. How? How would you set something like this up? Barrel flexing vs optical illusion? I am not a scientist. Also it is probable that my just assuming a practical explanation of the video on barrel and scope flexing would ruin any experiment. Bias. Oh well. Just the math would be beyond me. Yikes!

Just my feeble brain flexing does me in. Time for some cold orange juice. Very cold fortified orange juice.

 

[Boboclown]

By having every gun in your safe be shot on a bench with a high speed camera. If you want some real fun... Get an AR with a pencil barrel and see if you can flex it a little. Its easier if its already free floating.

 

[HB of CJ]

I wonder if there could be anyway to shoot off that gun without any sound waves hitting the camera at all. None. What would the camera then record? Dunno.

How about a long telephoto lens. Would that work? It would take quite some time for the sonic boom and sound shock waves to hit the camera. Humm.

Then THAT could eliminate the lensing or compression or distortion the camera would see? That would only leave the physical flexing of the barrel and scope?

But ... that would not eliminate all the potential optical illusions. Plus such very high speed video cameras do not rent cheap. The deposit would be huge.

Also thinking for this to work you would have to eliminate all the atmosphere around the gun at firing. A huge very high efficiency vacuum chamber. Oh boy.

 

[etrain16]

Its also not just the barrel that will flex, the entire rifle will flex. Some more than others, but you won't notice it because it happens too fast for you to see it. The only way you will notice is if you watch a slow motion video.

If you want to appreciate the stuff your optics go through:

I knew barrels had natural harmonics and did flex a bit, but in the video I posted in the OP, it seems the barrel flexed far more than I would have expected. I didn't see the same flex in the Barrett. I also noticed the barrel seems to flex in the direction opposite of the slant muzzle brake at the end of the barrel, so that seems to have a direct affect on the barrel flex.

 

[Boboclown]

I knew barrels had natural harmonics and did flex a bit, but in the video I posted in the OP, it seems the barrel flexed far more than I would have expected. I didn't see the same flex in the Barrett. I also noticed the barrel seems to flex in the direction opposite of the slant muzzle brake at the end of the barrel, so that seems to have a direct affect on the barrel flex.

The Barrett also had a thicker barrel. The slant brake pushes gas in the opposite direction to help the recoil (cause apparently it recoils up and right without it ).

 

[etrain16]

The Barrett also had a thicker barrel. The slant brake pushes gas in the opposite direction to help the recoil (cause apparently it recoils up and right without it ).

I always thought that slant brake was odd. When I got my first AK, I thought someone had put it on incorrectly.

 

[Kruel J]

I wonder if there could be anyway to shoot off that gun without any sound waves hitting the camera at all. None. What would the camera then record? Dunno.

How about a long telephoto lens. Would that work? It would take quite some time for the sonic boom and sound shock waves to hit the camera. Humm.

Then THAT could eliminate the lensing or compression or distortion the camera would see? That would only leave the physical flexing of the barrel and scope?

But ... that would not eliminate all the potential optical illusions. Plus such very high speed video cameras do not rent cheap. The deposit would be huge.

Also thinking for this to work you would have to eliminate all the atmosphere around the gun at firing. A huge very high efficiency vacuum chamber. Oh boy.

If it was the camera, the entire image would distort, not just the gun. And yes, that's what happens to firearms and optics under recoil. No fancy trick, no optical illusions. Just physics.

 

[Boboclown]

I always thought that slant brake was odd. When I got my first AK, I thought someone had put it on incorrectly.

The Russkies have a reason for their designs... They're a practical people. When I traded for the wasr I got a muzzle brake and a flash hider, replaced the muzzle brake on it with the slant brake. Never did test how well the other muzzle brake did, but the slant brake is simple and works so no reason to check.

 

[Kruel J]

Fast forward to about 6:14 for the slow mo. Pay attention to the handguards as well. No distortion to any other part of the video besides the rifle. It's not the camera.

 

[Boboclown]

When you see what happens to a rifle in slow motion, you really appreciate the amount of torture they go through just from being shot. The same thing for optics.