“BARREL MOVEMENT BEFORE THE BULLET EXITS”

[Edsel]

Bryan Litz’ video was demonstrating how a rifle barrel moves (or perhaps contracts?) by a little bit before the bullet even exits the barrel.

Is the apparent barrel movement:

(1) An artifact due to gases exiting before the bullet

(2) Secondary to the barrel metal behaving in a fluid state during high impulse, with the muzzle contracting rearwards while the areas proximal to the breech and throat are expanding sideways?

I suspect the latter…

During high impulse events, solids may exhibit properties more akin to liquids.

For instance, a bullet cratering on impact resembles the propagation of a water droplet…

 

[Edsel]

…just like in “The Matrix!”

 

[Edsel]

Looking into this would actually benefit from a real FEA exercise instead of some bubba spouting the word “harmonics” and “physics.”

 

[Edsel]

Another video suggests that the typically imagined “OBT Harmonics…”

…a phrase I casually throw around despite my really superficial understanding of it all…

…does not occur the way we suppose they do.

Perhaps this model’s a better representation?

EDIT:

(3) Secondary to a mass moving through the rifling? Can't really visualize how it would result in a rearward push, though.

 

[Edsel]

Just had an awful flashback…

Harmonics!!!

Oscillation!!!

Frequencies!!!

There was even this “moderator” on another forum claiming that something would “violate the laws of motion…”

Wow!

Brought to you by us bubbas who can’t even spell “muzzle brake” properly

 

[ma smith]

coriolis effect for sure

 

[Mike Casselton]

Just had an awful flashback…

Harmonics!!!

Oscillation!!!

Frequencies!!!

There was even this “moderator” on another forum claiming that something would “violate the laws of motion…”

Wow!

Brought to you by us bubbas who can’t even spell “muzzle brake” properly

It's Muscle Break. Duuurrrr!

 

[Csafisher]

Why would the barrel contract?

 

[AccuSol-ERN]

Regardless of the science at the micro level......there are external influences at the macro level that ultimately decide point of impact.

Over the years, I have seen too many shooters chasing the reloading minutia, while never learning/practicing shooting techniques that have a more substantial improvement on point of impact.

The science is neat to talk about, but lets face it......how much variability is there in barrel steel composition, barrel bore dimensions, barrel bore straightness, bullet jacket composition, bullet size, bullet true balance, environmentals, rifle peripherals, etc.

I look for patterns and trends. In my observation straighter barrels seemmore tolerant in absorbing the above variables. Also, I get measurably better chambers with conventional 4 groove barrels. Super consistant ammo makes tuning or seating depth easier/better. I don't have time to figure out the science.

Ern

 

[Edsel]

It's Muscle Break. Duuurrrr!

Ya mean, "It be called Muscle Break."

Thass raaaht!

 

[Edsel]

Why would the barrel contract?

Perhaps it be called Tacticle Detumescence, in warriertalk!

 

[Schütze]

I sure hope you get extra points for your efforts.

 

[Csafisher]

View attachment 8509179

View attachment 8509173

lol ok…..

 

[Im2bent]

View attachment 8508935

Another video suggests that the typically imagined “OBT Harmonics…”

…a word I casually throw around despite my really superficial understanding of it all…

…do not occur the way we suppose they do.

View attachment 8508936

Perhaps this model’s a better representation?

Potato.....potahto

 

[Secant]

Self image

Public image

Sometimes it be like that.
But don't worry scrotes, there are lots of tards out there living really kick ass lives.

 

[Edsel]

I don't have time to figure out the science.

Ern

Thet's why Litz be Litz, an' we be some no - account idjit bubbas!

And that's why every other rapidly developing country overseas is EASILY eating our lunch.

 

[E. Bryant]

Are we really going to get wrapped up in attempting to predict the deflection of a 1.35"-diameter steel rod during the first few milliseconds after firing pin impact when the rifle is being held by a twitchy bag of flesh?

 

[Edsel]

Are we really going to get wrapped up in attempting to predict the deflection of a 1.35"-diameter steel rod during the first few milliseconds after firing pin impact when the rifle is being held by a twitchy bag of flesh?

Twitch

Twitch

Twitch

Posting from the range...

Dang, it be gettin' cold 'ere an' there be shrinkage in th' netherplaces!

 

[cas6969]

This is easy enough to test. You just need to build a straight line test firing jig, mounted to a solid immovable base, and then buy an $80k slo-mo camera.

 

[R_A_W]

 

[powdahound76]

This is another example of why fools do fools errands “in the name of science!”



Focus on shooting with a bipod and rear bag, off a pack prone or seated, tripod, tree branch, fence post, etc and be a solid 5 shots at 1 MOA at 800-1000 yds shooter.

my old friend Foul Mike would challenge me to shoot paper at 600.
Excellent exercise. Harder than you think.
He never worried about this minutia and very likely took more cold bore 1000 yd shots with first round hits on a target 1 MOA in height and 1/3 MOA in width in a year, than most in their life.

 

[cas6969]

"If you're trying to do less than I'm doing, you're stupid. If you're trying to do more than I'm doing, you're stupid."

Standard internet answer.

 

[powdahound76]

Wrong again old man

 

[Edsel]

Yep!

Ah’m not hearin’ dem deer an’ coyotes complainin’ none, JimBob!…

 

[msgriff]

This is easy enough to test. You just need to build a straight line test firing jig, mounted to a solid immovable base, and then buy an $80k slo-mo camera.

They kind of already do that, except maybe the slo-mo camera part. Benchrest rail gun competitions are fascinating.

 

[joetuono]

Bryan Litz’ video was demonstrating how a rifle barrel moves (or perhaps contracts?) by a little bit before the bullet even exits the barrel.

Is the apparent barrel movement:

(1) An artifact due to gases exiting before the bullet

View attachment 8508908

(2) Secondary to the barrel metal behaving in a fluid state during high impulse, with the muzzle contracting rearwards while the areas proximal to the breech and throat are expanding sideways?

I suspect the latter…

During high impulse events, solids may exhibit properties more akin to liquids.

View attachment 8508915

View attachment 8508916

View attachment 8508913

View attachment 8508914

For instance, a bullet cratering on impact resembles the propagation of a water droplet…

The video is labeled “gun moves back from here” not “barrel moves back from here”. Going by just this I’m pretty sure the video is to demonstrate that the bullet is still in the barrel during recoil. Most people believe the bullet exits the barrel before recoil happens.

Could be wrong though, wouldn’t be the first time

 

[Edsel]

The video is labeled “gun moves back from here” not “barrel moves back from here”. Going by just this I’m pretty sure the video is to demonstrate that the bullet is still in the barrel during recoil. Most people believe the bullet exits the barrel before recoil happens.

Could be wrong though, wouldn’t be the first time

Yeah.

Sent a message over to Litz, asking if they had a video of the entire rifle...

Hopefully he'll respond.

It'd be interesting to see if everything moves rearward prior to the bullet exiting, as I've never seen a Bomb Calorimeter move during combustion

 

[gwood]

Gee, if only someone like Harold Vaughn had written a book about this 25 freakin' years ago...

 

[Edsel]

Gee, if only someone like Harold Vaughn had written a book about this 25 freakin' years ago...

We have someone of similar caliber who goes by "Varmint Al."

 

[Ronin22]

The price of tea in China means more...

 

[Sum Ting Wong]

Recoil begins as soon as the projectile starts to move. Newton’s third law.

 

[Im2bent]

Recoil begins as soon as the projectile starts to move.

Newton.......Are we talking about Newton?!?!?!?!??!?

 

[Csafisher]

View attachment 8509409

Yeah.

Sent a message over to Litz, asking if they had a video of the entire rifle...

Hopefully he'll respond.

It'd be interesting to see if everything moves rearward prior to the bullet exiting, as I've never seen a Bomb Calorimeter move during combustion

I’m not sure what you’re smoking. But it must be good.

 

[Im2bent]

I see they used a real mans caliber for the test.

 

[cas6969]

Newton.......Are we talking about Newton?!?!?!?!??!?

And a cold glass of milk. Mmm...

 

[E. Bryant]

They kind of already do that, except maybe the slo-mo camera part. Benchrest rail gun competitions are fascinating.

So when I remove the human behind the recoil pad, the error goes away, and when I add the human back in, then we start missing targets. Tells me that an academic exercise on barrel wobulation ain't the priority.

Now, as an engineer, I do find the postulated hypothesis of barrel deflection/distortion plausible and fascinating. There's certainly enough force involved to move things around, these forces reach a peak shortly after start of combustion (when the bullet is barely moving), and we know the barrel moves before the bullet leaves the muzzle because things get screwy if the barrel is not properly floated or pre-loaded. Understanding the deflection would be the first step towards reducing it. But the shooter is still the problem.

 

[DeathBeforeDismount]

 

[Im2bent]

And a cold glass of milk. Mmm...

Dude Oreos for the win!

 

[308pirate]

This is another example of why fools do fools errands “in the name of science!”



Focus on shooting with a bipod and rear bag, off a pack prone or seated, tripod, tree branch, fence post, etc and be a solid 5 shots at 1 MOA at 800-1000 yds shooter.

my old friend Foul Mike would challenge me to shoot paper at 600.
Excellent exercise. Harder than you think.
He never worried about this minutia and very likely took more cold bore 1000 yd shots with first round hits on a target 1 MOA in height and 1/3 MOA in width in a year, than most in their life.

What do you expect in a forum full of gear queers where the number of posts that start with "Whats the best bipod/bag/muzzle "break"/whatever" outnumber the ones asking "how do I get better at shooting" by 20 to 1?

 

[Baron23]

I didn't want to rain on @Edsel's parade but when I saw the Litz vid he posted I rather thought the rearward movement was more likely due to recoil...no matter the fixture....rather than linear compression of a heavy steel barrel. I'll be interested in the response if Litz answers Edsel's email.

I did find the post by Litz shown by @Csafisher to be interesting and indeed there is no visible vertical oscillation in that vid.

There does seem like a lot of discussion about using bullet speed to time the its exit at the top or bottom of a vertical oscillation (OBT). But, with a round barrel, if there were any oscillations that actually exist, I can't imagine any reason for them to be in solely the vertical plane...yeah, a vertical vector component and a horizontal vector component summing to some sort of movement at some angle.

Aside from just an academic interest, I'm sort of with all the guys who stress the shooter's influence over any of this harmonic stuff and certainly in my case the shooter's influence is orders of magnitude greater...cause I'm old and I suck. lol

Cheer guys

 

[hlee]

It'd be interesting to see if everything moves rearward prior to the bullet exiting, as I've never seen a Bomb Calorimeter move during combustion

God I hope you’re trying to be cute. A bomb calorimeter is a closed system.

 

[E. Bryant]

God I hope you’re trying to be cute. A bomb calorimeter is a closed system.

Now you've gotten me excited about the experimental component of this thought exercise.

 

[E. Bryant]

I didn't want to rain on @Edsel's parade but when I saw the Litz vid he posted I rather thought the rearward movement was more likely due to recoil...no matter the fixture....rather than linear compression of a heavy steel barrel. I'll be interested in the response if Litz answers Edsel's email.

I did find the post by Litz shown by @Csafisher to be interesting and indeed there is no visible vertical oscillation in that vid.

There does seem like a lot of discussion about using bullet speed to time the its exit at the top or bottom of a vertical oscillation (OBT). But, with a round barrel, if there were any oscillations that actually exist, I can't imagine any reason for them to be in solely the vertical plane...yeah, a vertical vector component and a horizontal vector component summing to some sort of movement at some angle.

Aside from just an academic interest, I'm sort of with all the guys who stress the shooter's influence over any of this harmonic stuff and certainly in my case the shooter's influence is orders of magnitude greater...cause I'm old and I suck. lol

Cheer guys

Let's say that there is some vertical component - "barrel whip" or whatever one wishes to call it. The action isn't symmetrical about the horizonal plane, so this is bound to arise. Having agreed upon that, what do we think is the magnitude compared to the vertical displacement induced by the rest of the system - namely the interfaces between the action and the stock, and the stock and the shooter?

We know that the combined effects of the barrel's intrinsic flex and the motion between the action and the stock is relatively small; 0.010" is usually considered enough to float the barrel. That's tiny compared to the displacement at the muzzle that can be observed from a shooter with less than optimum fundamentals.

I'm not suggesting that we discontinue pursuit of incremental gains at the margins because human sport is filled with success stories of exactly that type. Let's just make sure we're attacking the problems with the largest surface area first. Ultimately, I'm less concerned about barrel displacement in general than I am about displacement that isn't consistent shot-to-shot, and solving for the latter problem would typically require breaking down the problem to its fundamental elements to understand the variation and contribution of each. A large undertaking, for sure.

 

[Slides]

View attachment 8509409

Yeah.

Sent a message over to Litz, asking if they had a video of the entire rifle...

Hopefully he'll respond.

It'd be interesting to see if everything moves rearward prior to the bullet exiting, as I've never seen a Bomb Calorimeter move during combustion

Mount some laser interferometers around it, I'm sure you'll get detectable movement.

 

[MarinePMI]

We have someone of similar caliber who goes by "Varmint Al."

Is he still around? I haven't thought of the GGVG board in a dog's age....

 

[Edsel]

Oh, rats.

Bryan Litz says it’s “just recoil.”

 

[Csafisher]

Oh, rats.

Bryan Litz says it’s “just recoil.”

It says that in the first sentence of the fb post you attached………

 

[Edsel]

@Baron23

You can almost hear me sob!…

 

[E. Bryant]

Oh, rats.

Bryan Litz says it’s “just recoil.”

I mean, it's more than "just recoil" - it's just that the part of this that isn't recoil is almost immeasurable.

 

[kthomas]

Let's say that there is some vertical component - "barrel whip" or whatever one wishes to call it. The action isn't symmetrical about the horizonal plane, so this is bound to arise. Having agreed upon that, what do we think is the magnitude compared to the vertical displacement induced by the rest of the system - namely the interfaces between the action and the stock, and the stock and the shooter?

We know that the combined effects of the barrel's intrinsic flex and the motion between the action and the stock is relatively small; 0.010" is usually considered enough to float the barrel. That's tiny compared to the displacement at the muzzle that can be observed from a shooter with less than optimum fundamentals.

I'm not suggesting that we discontinue pursuit of incremental gains at the margins because human sport is filled with success stories of exactly that type. Let's just make sure we're attacking the problems with the largest surface area first. Ultimately, I'm less concerned about barrel displacement in general than I am about displacement that isn't consistent shot-to-shot, and solving for the latter problem would typically require breaking down the problem to its fundamental elements to understand the variation and contribution of each. A large undertaking, for sure.