Are bull barrels more accurate

[AK103K]

These were shot from a "heavy barreled" Remington 700V at 100 yards, prone off of a bipod. Both are 5 shot groups....

This was shot the same way at the same distance, with my "light barreled" Savage Scout. That group is 20 rounds shot over about 20-30 minutes....

Dont much get into all the formulas while shooting, get to much of that at work. I just shoot to forget about all that.

 

[splatman]

Yes Bart pressing the enter key a bad habit from the days of old.

 

[Jim Watson]

Yes that is correct A=dv/dt. So what
is da/dt ? (the time derivative of
acceleration). Well is has no
special name its just an acceleration
differential.

Some sources call the time rate of change in acceleration "surge."
I have seen it said that surge is behind much of motion sickness.

There is also some weird speculative physics wrapped around da/dt, "Davis Mechanics." But the Dean Drive still could not be replicated.

 

[splatman]

Brian, what you are calling "my original premise" was just a side note. If you want to call internal ballistics "gobblygook" do you have a special name for external ballistics? Just curious?

 

[dayman]

It has little to do with the subject of the thread, but da/dt does have a name. It's a "jerk", or a "surge".
Also, it's the derivative of acceleration, not a differential (unless you're intentionally talking about an infinitesimal change in acceleration without regard to time).
It feels the same as acceleration, just..... more (Like a " surge" or a "jerk").
Your space shuttle example has more to do with inertia than a change in acceleration.
When I'm not shooting, or arguing on the internet I actually teach calculus and introductory physics, so I do have some idea of what I'm talking about.
If you're right that the human body can't feel it that's something I've never heard, and goes against how the first 3 derivatives of position vs. time are generally introduced.

But back to the matter at hand; it seems like since thicker barrels flex less they're easier to tune, but not necessarily any more accurate than a tuned thin barrel.
Since easier to tune equates to cheaper, it would make sense that a lot of manufacturers would go that way.

 

[splatman]

The speculative physics concerning da/dt was popular 20 years ago and it was thought that it was a distinct sensation the body could detect which was different than what you would feel under a sequence of differential accelerations, but I dont think it exists.

 

[Brian Pfleuger]

Brian, what you are calling "my original premise" was just a side note. If you want to call internal ballistics "gobblygook" do you have a special name for external ballistics? Just curious?

Actually, I specifically said that all the acceleration business, whether or not a human can feel it (and they can), was irrelevant to your original premise.

I even said:

All of which is irrelevant to "Are Bull Barrels More Accurate?"

It is, however, not irrelevant that you are completely wrong about a subject that takes up almost half of your original post.

What I called "gobbledegook" was your theory/premise/post, whatever you want to call it. It's a bunch of irrelevant and/or unrelated and mostly incorrect statements, all of which (even if they were correct) have nothing to do with a bull barrel being more accurate.

I also don't believe that "the crown has slapped the bullet in the butt right before the bullet is airborne." Both the barrel and the bullet are in motion when the bullet exits the bore. The bullets momentum causes it to continue in whatever direction that both it and the bore were headed when it left. It does not get "slapped". That would imply that the barrels travel was faster than the bullets travel. Since they are in full contact with one another until the instant that the base of the bullet clears the muzzle, that is not possible.

I'll break it down for you:

At
this point the bullet is still accelerating but not as much as
when the bullet is say midway down
the bore.The mathematicians
understand this to be the time
derivative of acceleration da/dt.

True but irrelevent

As an interesting side note, the
human body can feel acceleration,
like when you jump out of an
airplane, but the body can not
detect its time derivative. In other
words the body cannot detect a
change in acceleration.

Not true, and totally irrelevant.

So getting
back to the internal ballistics at the
point when the bullet begins to exit
the muzzle. So as you know the
barrel is somewhere in its whip
dynamic. Now suppose you have
skillfully fine tuned your load and
the tip of the bullet clears the crown
at zero amplitude... ok thats great.

True, the barrel has a "whip dynamic". When the tip clears the muzzle is irrelevant and I've never seen any person reference that moment until this post.

Now here is what makes life interesting. Bullets have length so
what is happening when the tail
of the bullet clears the crown? Well
more than likely the muzzle is no
longer at zero amplitude. The
muzzle is undergoing a net acceleration in some direction
which is not longitudinal with the
static bore. It is as if the crown has slapped the bullet in the butt
right before the bullet is airborne.

Since the bullet and bore/muzzle are in full contact with one another, whatever velocity vector the muzzle has, the bullet ALSO has. The only way the muzzle would "slap" the base of the bullet is if the bullet was stationary (or much slower) relative to the muzzle and it is not.


However, what ultimately matters is the truth of the basic premise "Are Bull Barrels More Accurate." You can argue all the other stuff until you're blue in the face. The simple fact is that the answer to that premise is no, so none of the rest matters.

 

[barnbwt]

Of course bull barrels are more accurate; there's a reason heavy machine gun barrels are enormous and it isn't just for fun. More barrel meat means more volume to dump thermal energy into before the barrel overheats and is toast.

So bull's do have a purpose, just not one that most shooters have cause to care much about

TCB

 

[JohnKSa]

A change in acceleration is referred to as a "jerk" and can absolutely be felt by the human body.

This is correct in substance and specifics. Humans can feel it and it is often referred to as "jerk".

http://physics.info/kinematics-calculus/

"This makes jerk the first derivative of acceleration, the second derivative of velocity, and the third derivative of displacement."

"Jerk is not just some wise ass physicists response to the question, "Oh yeah, so what do you call the third derivative of displacement?" Jerk is a meaningful quantity.

The human body comes equipped with sensors to sense acceleration and jerk. "​

http://math.ucr.edu/home/baez/physics/General/jerk.html

" It is a little less well known that the third derivative <of position>, i.e. the rate of change of acceleration, is technically known as jerk (symbol j). "

"As its name suggests, jerk is important when evaluating the destructive effect of motion on a mechanism or the discomfort caused to passengers in a vehicle."​

http://en.wikipedia.org/wiki/Jerk_(physics)

"In physics, jerk, also known as jolt, surge, or lurch, is the rate of change of acceleration; that is, the derivative of acceleration with respect to time..."

"Even where occupant safety isn't an issue, excessive jerk may result in an uncomfortable ride on elevators, trams and the like, and engineers expend considerable design effort to minimize it."​

The mention of elevators is instructive. Elevator designers are very concerned with minimizing jerk because humans generally find it more uncomfortable/disturbing than constant acceleration.

http://www.gaudisite.nl/ElevatorPhysicalModelSlides.pdf

"humans feel changes of forces
high jerk values are uncomfortable"​

http://www.lift-report.de/index.php/news/176/368/Elevator-Ride-Quality

" The variable experiences are changes in the effect of gravity on the human body caused by acceleration, deceleration, jerk and also noise and vibration generated by the elevator systems."

"Jerk – The rate of change of z-axis acceleration, attribute to lift motion control and expressed in metres per second cubed (m/sec3)."

"Jerk is probably the most important of the elevator variables and the most difficult to quantify when defining overall elevator ride quality. The human body responds very quickly to rates of change in acceleration..."​

The speculative physics concerning da/dt was popular 20 years ago and it was thought that it was a distinct sensation the body could detect which was different than what you would feel under a sequence of differential accelerations, but I dont think it exists.

It certainly exists, it's not speculative and while it may have been "popular 20 years ago" the implication that it has somehow waned in "popularity" since then is misleading, at best.

The idea that da/dt (i.e. "jerk" or change in acceleration) can't be felt by humans is absolutely false.

 

[splatman]

Ok lets parse this one at a time:

>>
At
this point the bullet is still accelerating but not as much as
when the bullet is say midway down
the bore.The mathematicians
understand this to be the time
derivative of acceleration da/dt.
True but irrelevant
>>
Sorry not irrelevant. When the bullet accelerates there is a force; F=MA.
This force causes recoil, heat, barrel whip… all of which are relevant.



>>
As an interesting side note, the
human body can feel acceleration,
like when you jump out of an
airplane, but the body can not
detect its time derivative. In other
words the body cannot detect a
change in acceleration.
Not true, and totally irrelevant.
>>

This I will admit is very confusing so that’s my error. Its obvious that if you can feel a constant acceleration you can also feel a change in acceleration. When you jump from a plane you are under a constant 1G acceleration for the most part if you eliminate wind drag. If you are in a fighter jet you will experience a range of accelerations. You can call it jerks, surges or whatever you want but what it ultimately boils down to and what you can sense is your body being subjected to a change in velocity (by definition acceleration.) Not totally irrelevant, because it gives you a better understanding of the forces the bullet is undergoing.



>>
So getting
back to the internal ballistics at the
point when the bullet begins to exit
the muzzle. So as you know the
barrel is somewhere in its whip
dynamic. Now suppose you have
skillfully fine tuned your load and
the tip of the bullet clears the crown
at zero amplitude... ok thats great.
True, the barrel has a "whip dynamic". When the tip clears the muzzle is irrelevant and I've never seen any person reference that moment until this post.
>>

So this has never crossed your mind before? Try thinking out of the box once in awhile. This is certainly relevant, it takes time for the bullet to clear the crown and a lot of stuff happens during this time interval, you have barrel whip going on, your barrel is already in recoil, the bullet is rotating at about 35000 rpm causing a torgue. The top shooters try to time their bullets to exit the muzzle when these factors are minimal.



>>>
Now here is what makes life interesting. Bullets have length so
what is happening when the tail
of the bullet clears the crown? Well
more than likely the muzzle is no
longer at zero amplitude. The
muzzle is undergoing a net acceleration in some direction
which is not longitudinal with the
static bore. It is as if the crown has slapped the bullet in the butt
right before the bullet is airborne.
Since the bullet and bore/muzzle are in full contact with one another, whatever velocity vector the muzzle has, the bullet ALSO has. The only way the muzzle would "slap" the base of the bullet is if the bullet was stationary (or much slower) relative to the muzzle and it is not.
>>>

You are not grasping the physics here. The bullet and bore/muzzle are NOT in full contact. A force is applied to the tail of the bullet which is not even close to the bullets center of gravity, this causes a torque on the bullet and can cause your bullet to key hole on paper. I bought some 357 magnum reloads from a gun shop and they key hole at 15 feet due to severe recoil. Other ammunition shoots great.

>>>
However, what ultimately matters is the truth of the basic premise "Are Bull Barrels More Accurate." You can argue all the other stuff until you're blue in the face. The simple fact is that the answer to that premise is no, so none of the rest matters.
>>>


Its obvious you do not know the meaning of the word premise. A premise is a statement that is assumed to be true. A question can not be a premise. “Are Bull Barrels More Accurate” is a question. Perhaps the omission of the question mark confused you.

 

[Brian Pfleuger]

Sorry not irrelevant. When the bullet accelerates there is a force; F=MA.
This force causes recoil, heat, barrel whip… all of which are relevant.

Sorry, but that force doesn't cause those things. Momentum is responsible for recoil. Different equation all together. That one is f=Δp/t. The heat comes from the energy of a chemical reaction or friction, not from F=MA. Barrel whip also does not come from F=MA. Barrel whip comes from the explosion of the powder, very much the same way that striking a pipe with a tuning fork causes a vibration in the pipe.

It's actually extremely complicated, but one thing that has nothing to do with it, directly, is acceleration.

Not totally irrelevant, because it gives you a better understanding of the forces the bullet is undergoing.

It is totally irrelevant to whether or not a bull barrel is more accurate. Totally. The bullet undergoes massive acceleration, much higher than most people would expect, but it's acceleration has *zero* to do with what type of barrel is more accurate. (Incidentally, a very fast bullet can experience over 300,000 Gs)

So this has never crossed your mind before? Try thinking out of the box once in awhile. This is certainly relevant, it takes time for the bullet to clear the crown and a lot of stuff happens during this time interval, you have barrel whip going on, your barrel is already in recoil, the bullet is rotating at about 35000 rpm causing a torgue. The top shooters try to time their bullets to exit the muzzle when these factors are minimal.

The top shooters do not time the tips exit and no one else does either. No one cares when the TIP exits. The body is still in contact with the barrel. No one cares about the tip. I never said that loads aren't tweaked for bullet exit. In fact, I have many times pointed folks to Dan Newberry's OCW load development technique, which I first learned about from UncleNick.

That technique (and all the others) have *zero* to do with when the tip of the bullet exits the barrel.

You are not grasping the physics here. The bullet and bore/muzzle are NOT in full contact. A force is applied to the tail of the bullet which is not even close to the bullets center of gravity, this causes a torque on the bullet and can cause your bullet to key hole on paper. I bought some 357 magnum reloads from a gun shop and they key hole at 15 feet due to severe recoil. Other ammunition shoots great.

You sir, are the one who does not understand what's happening. Bullets keyhole because they do not have sufficient rpm to stabilize them against aerodynamic forces. It has nothing to do, *NOTHING*, with the barrel "slapping" the bullet. They don't keyhole due to recoil either.

Its obvious you do not know the meaning of the word premise. A premise is a statement that is assumed to be true. A question can not be a premise. “Are Bull Barrels More Accurate” is a question. Perhaps the omission of the question mark confused you.

The title of the thread is a question... your treatise is a PREMISE... a proposition supporting or helping to support a conclusion. The ending statement "if you are considering pushing the accuracy envelope, consider the bull barrel." is a CONCLUSION and/or suggestion based on the conclusions that we're supposed to arrive at based on your PREMISE.

Your premise (all of them) are either faulty or irrelevant.

 

[4runnerman]

WOW--pant pant pant. Um--I think this is going the wrong direction here. The simple question was-- Are Bull barrels more accurate. I think we have almost all agreed( all things being equal) NO they are not. To many other things come into play- Which is why we say ( All things being equal ).

 

[splatman]

You say recoil is due to momentum. Your equation for momentum is incorrect. Momentum is mass multiplied by velocity. Where do you think velocity comes from? Velocity is attained from force, which is generated by pressure, which is generated by expanding hot gases, your not connecting the dots. By the way powder does not explode.

 

[Jim Watson]

The simple question was-- Are Bull barrels more accurate. I think we have almost all agreed( all things being equal) NO they are not.

Are we letting classroom physics and brag targets overrule a century or so of experience and empiricism? When have successful target shooters used light profile barrels when not required by rule? The bull barrels shoot better targets, day in day out.

 

[4runnerman]

Jim- They don't use thin profile barrels due to the amount of shots being taken and the barrels heating up. Cold barrel to cold barrel A heavy barrel will not out shoot a thin barrel ever. This is why I said all things being even. There is a million different tangents you could take off on about this subject as to why. But the truth is Heavy barrels are not more accurate,they hold on to accuracy longer,are easier to shoot more accurate,have less recoil,heat up slower,ect,ect, but ALL THINGS BEING EQUAL are not more accurate.

 

[Bart B.]

When have successful target shooters used light profile barrels when not required by rule?

Whenever they want to shoot their iron-sighted Palma rifles with 5-pound 30-inch .308 Win. barrels instead of 7-pound 30-inch and caliber magnum barrels in scoped rifles. And both shooting 25 shots in 15 minutes or thereabouts; one shot every 30 to 45 seconds. I've done that myself.

Since 1991, when Sierra introduced its 155-gr. 30 caliber bullet in .308 Win cases to comply with international rules, folks building and testing their rifles with long, skinny 5- and sometimes 6-pound barrels in weight-limited rifles get 1000-yard 15- to 20-shot test groups no worse than 6 inches. That's the size of 20-pound barrels' groups in 1000-yard benchrest rifles. No difference in inheirant accuracy between them.

 

[Picher]

It seems that we have too much physics and not enough practical rifle/load tuning here.

If we handload, we have the means to choose case brands, primers, powder types, and adjust powder charges, bullet seating depth, etc. to achieve a tuned load that exits the muzzle when the muzzle is nearly stopped in it's vertical movement. That's either nearly at the highest or lowest point. Most people agree that it works best when the muzzle is at the apex (the top) of it's cycle. The muzzle is at maximum transverse velocity when it's at the middle of its cycle, so variations in bullet velocity can result in worse-case groups. (The barrel also vibrates in other directions, but the vertical vibration is considered greatest, provided the barrel doesn't touch the forend.)

For people who don't handload, finding a particular factory ammo that groups well, also works. The Browning BOSS also works to tune the barrel to a particular ammo.

Finally, placing a movable pressure point in the barrel channel can tune a rifle for a particular ammo, but changes in hold, rest location, etc. may affect POI and group size.

 

[Bart B.]

If we handload, we have the means to choose case brands, primers, powder types, and adjust powder charges, bullet seating depth, etc. to achieve a tuned load that exits the muzzle when the muzzle is nearly stopped in it's vertical movement. That's either nearly at the highest or lowest point. Most people agree that it works best when the muzzle is at the apex (the top) of it's cycle.

Interesting theory, but not what's been proved to work best.

Browning claims their BOSS works that way; exiting when the muzzle axis is at an extreme of its arc. But they've not proved it by timing barrel whip movement with accelerometers and bullet exit by sensors connected to a system to do so; it's just theory they cannot back up with facts.

Bullets exiting the muzzle on its way up and close to the high point is probably the best place to tune loads for. But anywhere on its muzzle angle upswing is good enough. That way, slower ones (they all don't go out at exactly the same speed) leave later at a higher angle. Otherwise, why would the same lot of Federal .308 Win match ammo shoot very accurate at both 300 and 600 yards in barrel lengths from 22 to 28 inches both whippy and stiff?

Compensation for their greater drop down range makes them strike the same place as faster ones leaving at lower angles that won't drop as much. If all shots leave around the muzzle's highest angle, half of them (the slower ones) will not have their exit speed compensated for as they leave while the muzzle angle's going down. Down range groups will get bigger. The reverse happens if they leave about the muzzle axis lowest angle. We've not quite reached zero spread in muzzle velocity.

http://www.varmintal.com/apres.htm

The Brits proved this over a century ago:

https://archive.org/details/philtrans05900167

Even M14NM rifles shooting M118 match ammo had a bit of compensation. At 300 yards, their test group's vertical shot stringing was more than that at 600 yards. And muzzle velocities used in trajectory calculations didin't match bullet drop on paper. Evidence faster bullets left earlier on the muzzle axis up swing than slower ones did. They figured it was the gas port about mid point in the barrel making that part of the barrel bow up as gas escaped into the cylinder which made the muzzle axis point lower.

 

[Brian Pfleuger]

You say recoil is due to momentum. Your equation for momentum is incorrect. Momentum is mass multiplied by velocity. Where do you think velocity comes from? Velocity is attained from force, which is generated by pressure, which is generated by expanding hot gases, your not connecting the dots. By the way powder does not explode.

That's proof that you don't know what you're talking about. There are several equations for momentum. p=mv is only one of them. What is velocity? V=d/t. That means momentum is also p=md/t. Equations can be solved for any variable and variables can be substituted by the variables in other equations solved for them. One such equation is f=Δp/t. That also means that Δp=ft. Which makes perfect sense, the change in momentum is equal to the amount of force applied multiplied by the time it was applied.

You're spinning your wheels. Last post, you said this all came from f=ma. Now it comes from p=mv?

By the way, your attempts to deflect attention from the errors of your statements with petty trivialities like premise versus question and gunpowder exploding versus burning are not helping you look better.

I'm done here. You *clearly* have no idea what you're talking about and I'm not wasting any more of my life arguing with you about it.

Oh, and lastly, none of this has any real bearing on what barrel profile is most accurate.

 

[barnbwt]

"I bought some 357 magnum reloads from a gun shop and they key hole at 15 feet due to severe recoil."
Ummm, no. Keyholing comes from insufficient aerodynamic stability, usually due to insufficient spin. This can be due to insufficient barrel twist, insufficient velocity, undersized bullet diameter (or other reasons causing poor bullet/rifling engagement), unbalanced/misshapen bullets (hot loads can certainly deform soft lead, or thin-jacketed bullets). For the barrel itself to contact the rear portion of the bullet* (or whatever you are describing) it would have to be vibrating/recoiling several times faster than what the bullet is doing (based on the boat-tail taper). In which case a bull barrel's added stiffness would be worse. But, bull barrels tend to hold tighter groups than a thin barrel, given equally unturned ammunition, because barrel whip doesn't impart an off-axis force vector of consequence to the bullet as it leaves (a bad crown does)

In reality, when a barrel whips, it just redirects the bullet. And as can be seen for the variance in impact points for various loads (accounting for bullet drop) it really ain't that big of an amplitude at the end of the day; fractions of an inch projecting out to be mere inches at 100 yards at worst. As with all accuracy-effecting phenomenon, people's awareness of it greatly magnifies its actual importance. Even if the rear of the bullet was 'tipped' somehow, it is spinning so fast that it would probably not deviate much from it's travel vector; it would shift perpendicular to its axis only and continue on a parallel path, since it has such incredibly high rotational inertia upon exit.

TCB

*This sounds like the physics of that terrible Wanted movie. You can't throw bullets around corners any easier than you can tumble them by shaking the muzzle