Hey /k/
I'm at university doing a forensic science elective. Just had an exam that I almost got 100% on, but fucked up on 1 question single question.
The question was
>True or False: Rifling is a series of helical lands and grooves along the length of the gun barrel that improves the trajectory of a bullet.
For some reason, I thought rifling was specifically for accuracy, and I thought accuracy and trajectory were two different things. That said I am still a little confused. Is this question worded correctly or am I just being a dumb shit?
>>30212830
you can always ask the professor/test proctor for clarification. and it helps both.
>>30212830
>helical
False because only glock does this, everyone else is normal.
>>30212830
It's an oddly phrased question, but if you said false I understand why you got it wrong.
Think about it this way: Rifling does improve the trajectory of a bullet. If there was no rifling the trajectory would be shit.
Rifling spins a round to keep it stable, otherwise it'd tumble and it wouldn't have the same trajectory and range.
>>30212830
It improves accuracy due to the increase in momentum, and trajectory due to the bernoulli effect IIRC. Makes trajectory flatter.
>>30212830
Rifling provides spin stabilization to the projectile. This provides a consistant aerodynamic profile in flight aiding both accuracy and trajectory. Bullets tumbling through the wont fly as predictably and will bleed velocity faster thus worsening their trajectory.
>>30212830
So you did not think, "Improving trajectory"was related to overall accuracy? Then how are you going to match casings to firearms now CSI?
>>30212830
>That said I am still a little confused. Is this question worded correctly or am I just being a dumb shit?
It's worded correctly. Trajectory is just the path an object takes. Rifling improves the trajectory by stabilizing the bullet.
>>30212845
Don't Lee Metfords and Arisakas have similar rifling?
>>30212830
Uh, you're being an idiot.
Rifling improves accuracy. But how? By causing the bullet to spin, stabilizing it, making trajectory flatter.
You'll be more accurate with a better trajectory, makes sense?
>>30212901
>due to the increase in momentum
Wat
>>30212830
Thats not how bullets go.
>>30212845
"helical" means "in a twisty pattern". You're thinking of "polygonal".
>>30212957
>>>30212830 (OP)
>Uh, you're being an idiot.
>Rifling improves accuracy. But how? By causing the bullet to spin, stabilizing it, making trajectory flatter.
No stupid it doesn't make the trajectory flatter, velocity does that. Rifling only makes trajectory more consistent
You cant have accuracy without good trajectory
That question is flawed
Rifling affects
Twist Rate
It all affects how fast and the drop (trajectory of a projectile)
Theres no way you can have good accuracy without good trajectory. Its all goes hand it hand and it all has to do with the rifling.
Its too meta
>>30212845
Helical means in a circle you dumb fuck
>>30213049
Velocity makes it shoot flatter and have a better trajectory. It all feeds into one another.
Its like saying "What happens when you lift weights when working out?"
A. You gain muscle mass
B. You get stronger
C. You burn fat/calories
D. You tax your nervous system
ITS FUCKING META
>>30213049
So then rifling does "improve" trajectory then?
>>30212957
>making trajectory flatter.
This.
Plus, without spin, the bullet tumbles. Tumbling increases drag and makes the bullet drop sooner. Since there is no way to control the tumble, the drag is inconsistent and the trajectory not only becomes less flat (more drop) it becomes less consistent.
>>30213086
E. You fuck bitches.
F. You get money.
>>30213087
Of course since an improved trajectory is A FLATTER ONE.
I mean we are talking about guns and accuracy here, right?
Is this question about catapults?
>>30213086
>>>30213049 (You)
>Velocity makes it shoot flatter and have a better trajectory.
Is that not what I just said. If you had a bullet with a million fps, out of a smooth bore, it would still have a pretty flat trajectory
>>30212845
Not only are you retarded, but even your explanation of only glocks having [circular barrels] is wrong, lots of other brands have polygonal rifling.
>>30213087
Technically yes it does.
>>30213103
No, rifling stabilizes a bullet with its twist rate so that it goes as fast as it can without wobbling and creating drag
which in turn makes it shoot flatter
>>30212830
>I'm at university doing
if you made that infograph, you realllly dont belong at a university.....you belong at a day camp for people with foam helmets.
>>30213126
I dont know about smooth bores. All i know that how the rifling twist stabilizes a bullet and makes it shoot flatter
This is why some rifle twists/rifling is better for different grains
>>30213126
Actually i dont think it would because the bullet wouldnt be stabilized as much as a rifles barrel
But yeah it ita going a million fps its gonna be pretty flat out of a smooth bore
And out of a rifled one even flatter
>>30213164
its from google m8, i picked the first thing i saw, i dont have a meme folder
>>30213049
Yes it does make the trajectory flatter.
A conical bullet requires rifling, otherwise it will tumble. A stabilized conical bullet has a lower ballistic coefficient than a ball, or a tumbling conical, so it loses less velocity as a function of time.
It also drifts less in a given wind.
Rifled barrels were a significant development in small arms due to enabling conicals. Powders and barrel metallurgy didn't change so chamber pressure and thus velocity didn't increase until much later.
Holy shit does no one know anything about physics?
The thing that makes a bullets, or any projectiles trajectory flat is speed, the reason is simple. Gravity is always 32.2 ft/s^2 down, this is constant. So no matter how fast the bullet goes, as a function of time it will drop the same amount.
So with high velocity, the bullet will travel further away as a function of time. A 100fps bullet would be further away when it hits the ground than a 50 fps bullet. But they will hit the ground approximately at the same time (i say approximately because terminal velocity and y components).
Now it gets complicated, the thing that effects velocity for a bullet is (mostly) drag, there are some minor pressure forces but don't worry about them.
Look at this MATH: Fd = (p cd a v^2) * (1/2)
P is actually Rho, a greek alphabet for density, which is fairly constant, ignoring temperature, pressure, humidity etc differences.
v is velocity.
Two significant parts of this equation are the cd or drag coefficient and a which is area. These are judged entirely on the objects geometry relative to the air flow. This is why tumbling is bad, because there is more drag on the bullet at different points as it tumbles, since cd and area keep changing.
This is why bullets where once balls, because balls have a constant geometry no matter where you look at them.
This is why we spin a bullet, to keep the lowest drag and conserve as much velocity as possible. The reason a spinning bullet stays pointing in one direction is due to the gyroscopic principles. A gyroscope orientation is fixed in space, so the bullet stays pointing forward. Why a gyroscope does that? Conservation of angular momentum, that's all i'm qualified to say.
>>30212830
that pic is 7 levels of wrong
>>30213983
This is basically what I told these tards earlier. I just didn't science quite so hard
>>30212830
False. Rifling is not always "lands and grooves"
And "improving the trajectory" doesn't make any fucking sense.
It improves the accuracy yes, but I think of "improved trajectory" as flatter trajectory which rifling does nothing to affect.
Your professor probably got D's in English class.
>>30212901
>rifling
>Bernoullis principal
Yah nah. This isnt a carburator.
You might be thinking magnus effect, but that isnt even correct. Magnus effect is the reason bullets drift.
Bullet stabilization is via gyroscopic stability.
>>30212830
>lands and grooves
Polygonal barrels don't have them.
>>30212830
There was a true or false question on a high level University test?
>>30212975
The spinning caused by the rifling imparts angular momentum that would not be present if the bullet were just flung out of a smoothbore.
>>30214280
My aerobatic professor once told me any time it's a multiple choice or true and false, it's less of a test on the subject and more how well you can read.
>>30217065
*aeronautics
>>30212876
>Rifling spins
Did I winz?
>>30217065
As someone who studies a subject that involves a lot of bullshit pseudoscience, I assure you that that is correct.
(Paedagogics&Teaching, btw)
It doesn't help that German is THE one language that is actually designed to make a sentence's structure as obfuscated and complex as possible. I once wrote a sentence that was over 200 words long. Yes, two HUNDRED.
So yeah. Make up one of those. Actually, make up ten of those. In half the exams, randomly smuggle a couple of "not"s into the sentences. Boom. Easy SC-test, easy to correct (from an instructor's perspective), not a lot of room for discussion (as opposed to written answers, for instance).
>>30212975
He means increase in rotational momentum. The bullet will spin clockwise (from the shooters perspective) which then by using the right hand rule cross products shows ghe rotational momentum vector in the direction of travel towards the target.
>>30212830
Thats...very oddly worded. However, stabilizing the spin of a bullet reduces air resistance. The bullet is always hitting the air nose on and that helps the trajectory.
If you get a bad grade you can argue about semantics.
What does rifling do when a ball is used?
The minieball became a thing long after the rifle, so I'm confused.
There is no (meaningful) impact that rotational momentum has on maintaining orientation, it's a sphere. And rotational momentum wouldn't impact translation.
The rotation is perpendicular to the direction of travel, so it shouldn't provide any vertical forces.
Does it create 'pocket' of rotating air around the bullet decreasing resistance by the bernoulli principle, thereby making a flatter trajectory?
Basically I don't get why a rifle works with ball bullets. Can anyone help?
>>30220026
The minie ball was not an actual ball.
Rifling has no positive effect on a ball, however backspin can. Backspin will introduce the magnus effect in an upwards motion. This can be demonstrated with paintball markers. (See flatline barrel for model 98)
>>30220118
>The minie ball was not an actual ball.
I know. But it was developed after the rifle, wasn't it?
>Rifling has no positive effect on a ball, however backspin can.
Yep. Any knowledge of a firearm that has done this?
>>30220186
Yes, but the rifling was created as a means to launch the projectile.
The idea was that the minie ball would wound better, and ballistics werent a well known science back then. Turns out that a stabilized elongated projectile has a better bc than a ball.
>>30220186
Not to my knowledge, no.
>>30220186
>>30220118
>Magnus effect to stabilize bullets
I assume you mean to counteract gravity thus have a flatter trajectory?
This would work, in theory, since the magnus effect has been used to generate lift in places and such. The problem is, while the effect can be used to generate a massive amount of lift, it also creates CRAZY induced drag.
Induced drag, is drag as a byproduct of lift, whenever and wherever lift is generated, induced drag is created.
So while the bullet would start climbing up, pretty rapidly, it would slow down compared to the ground much faster and wouldn't get as far as you'd hope.
D = L^2 / PV^2 Ae(ar)(pi)
p is density, v is vilocity, A is area, e is a constand, ar is aspect ratio and pi is a constant.
L is lift, as lift goes up, so does the drag.
So in summery, yea the bullet could be made so that the force of gravity and the lift balance out, but any amount of lift you make, is going to bleed away your forward motion. Physics, there is no free energy.
It's also just easier to make grooves that spin a cone than to precisely machine something to shoot a ball JUST right so that its Fl = Fg.
Also magnus effect wouldn't help with drift, like the gyroscopic principle does.
>>30220602
Pretty much.
Atleast with paintball markers it extended the range considerably, but there are other problems with a purposefully induced magnus effect like that.
You must have your rifle perfectly verticle, or that same magnus effect will pull your shots.
With a heavy round projectile, you would really need to spin that sucker fast to counteract gravity. Unrealistically fast.
