on call? - Page 3 - M14 Forum

M14 Forum


on call?

This is a discussion on on call? within the Accuracy forums, part of the M14 M1A Forum category; For PublicSafety400: Regarding your physicist's statement about recoil, I don't understand where he states that the firearm doesn't move until the bullet is gone from ...


Go Back   M14 Forum > M14 M1A Forum > Accuracy

78Thanks
Reply
 
LinkBack Moderator Tools Display Modes

Old December 29th, 2016, 07:19 PM   #31
Platoon Sergeant
 
shooter86314's Avatar
 
Join Date: Dec 2013
Location: arizona
Posts: 352
off topic

For PublicSafety400: Regarding your physicist's statement about recoil, I don't understand where he states that the firearm doesn't move until the bullet is gone from the barrel.

I am a bit rusty about conservation of momentum, whether in a firearm or in a small boat, but I am very confident that the firearm begins to recoil immediately as the bullet starts to move.

Thanks from JEFFJP_N_JJ

Last edited by shooter86314; December 30th, 2016 at 01:49 AM.
shooter86314 is offline  
Remove Ads
Old December 30th, 2016, 08:36 AM   #32
Fire Team Leader
 
eagle0199's Avatar
 
Join Date: Jul 2008
Location: Louisiana
Posts: 180
When I first started shooting highpower, my coach would have me call the shot, then he would also call it based on the bullet trace. He was right a lot more often than I was. I thought (and still think) he was using some "magic" in his coaching.

eagle0199 is offline  
Old December 30th, 2016, 12:32 PM   #33
Dodgin' The Reaper
 
Ted Brown's Avatar
 
Join Date: May 2004
Location: Jacksonville, OR
Posts: 5,472

Awards Showcase

Remember coaches Rule number four: If you are assigned the worst shooters on the range for a big team match, consider yourself lucky. Who can question your ability when your shooters are firing misses in all directions.

Ted Brown is offline  
 
Old December 30th, 2016, 12:44 PM   #34
Scout Sniper
 
DudleyDR's Avatar
 
Join Date: Aug 2009
Location: Idaho
Posts: 784
Quote:
Originally Posted by shooter86314 View Post
For PublicSafety400: Regarding your physicist's statement about recoil, I don't understand where he states that the firearm doesn't move until the bullet is gone from the barrel.

I am a bit rusty about conservation of momentum, whether in a firearm or in a small boat, but I am very confident that the firearm begins to recoil immediately as the bullet starts to move.

You are right.

Whoever that "physicist" is, if that is his statement, then he is either ignorant of or dismissive of Sir Isaac Newton's third law of motion:

"When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body." Equal and opposite...at the instant the force is applied. No need to overthink this.

As soon as a projectile starts moving forward from its resting place the firearm moves in an opposite linear rearward direction. End of story. Whenever the projectile leaves the barrel is irrelevant to the equation.

Much of the "opposite direction" force is absorbed by the larger mass of the firearm as compared to the weight of the projectile.

Thanks from JEFFJP_N_JJ

Last edited by DudleyDR; December 30th, 2016 at 06:22 PM.
DudleyDR is offline  
Old December 30th, 2016, 01:05 PM   #35
Platoon Sergeant
 
Join Date: Dec 2012
Location: Comanche, TX
Posts: 357
Quote:
Originally Posted by PublicSafety400 View Post
Not disputing that practice makes perfect. I'm just disputing the need to call your shot in order to reach perfection in all circumstances and methods of shooting. i am able to practice all of the proper shooting techniques and control and hopefully will improve as time goes by. My point was that when bench shooting with bipod or sandbag there is very little perceptible movement of the crosshairs on the target that can be detected before or while the shot goes off. I agree with the comment of someone earlier that there is much more opportunity to see where the aim point has moved to when you pull the trigger and so I see the value of calling the shot in those circumstances. And yes I absolutely believe in proper control while practicing. I once mentioned on this forum that I can spend an hour at the range and only expend 20 rounds. That is my way but not necessarily what others are about. I take my time and try to make every shot count. I am not about competition with others but I'm in competition with my self.

Enjoyed the discussion.
PublicSafety400, I've read through your posts on this topic, and I can see you're not onboard with the advice given by most of the commenters here.

Not trying to be sarcastic, but what kind of scores do you typically shoot? (You don't need to tell us, but if you want to improve, you do need to be honest with yourself)

Unless you're shooting all x's every time out, you have room for improvement.

I mostly accept what you're saying about the bullet striking your point of aim most of the time. (how you really know that, BTW, if you're not calling your shot?) If your scores aren't perfect, why not? Is it b/c your point of aim isn't in the center of the bullseye? Or perhaps you cause the rifle to move a little when you squeeze the trigger. If your aim isn't perfect, why isn't it? And what do you need to do to improve it?

Calling your shots is not just about managing the wobble. It's also about making your point of aim more perfect and improving trigger control.

I'm not an expert shooter- there are plenty of people on this forum who can shoot better than I. But, I've worked pretty hard on my marksmanship, I've learned a lot, and I've improved significantly. One of the things I've come to believe in is calling my shot each time, including dry firing, for all positions.

Evil Incarnate is offline  
Old December 30th, 2016, 07:54 PM   #36
Newbie
 
Lon B's Avatar
 
Join Date: Oct 2016
Location: Winton CA
Posts: 9
Well I read a lot of this thread but not all of it. Certainly somebody mentioned that calling your shot helps to keep you from anticipating the shot or flinching. It makes you concentrate (follow through) long enough for the bullet to leave the barrel.

Thanks from DudleyDR
Lon B is offline  
Old December 30th, 2016, 10:25 PM   #37
Scout Sniper
 
DudleyDR's Avatar
 
Join Date: Aug 2009
Location: Idaho
Posts: 784
Calling a shot has always been a fundamental training exercise for as long as I can remember. Just like "B.R.A.S.S." (Breathe, Relax, Aim, Sight, & Squeeze), a marksman needs to know just where his round is going or went - where his last sight alignment & sight picture was directing the bullet. It is part of the concentration and focus in analyzing one's skill progression. It is like a follow-through swing in baseball or golf. Ignoring fundamentals is akin to receiving a "participation trophy" while you waste time and ammo. Regards.

DudleyDR is offline  
Old December 31st, 2016, 05:44 AM   #38
Doc
Lifer
 
Doc's Avatar
 
Join Date: Dec 2011
Location: MS
Posts: 3,373
Lots of good statements in the post above.
Being able to call he shots is critical to improving scores. It basically expands/describes/magnifies/empathizes/demonstrates/et cetera - the ability pf the shooter to "hold" and understand the exact "sight picture" and feel of follow through as the shot is executed. An accurate rifle and accurate, trained shooter should have the confidence to know if an errant shot was due to a change in conditions or a "poor hold/follow through by the shooter ----- the shooter not being able to do that wlil greatly hinder a coaches ability to help the shooter correct for changing conditions.........

Thanks from DudleyDR
Doc is offline  
Old January 1st, 2017, 09:10 AM   #39
Automatic Rifleman
 
Join Date: Sep 2016
Location: Texas
Posts: 131
Well, I'm willing to take the word of a physicist over the limited knowledge of all the M14 experts here. Here is a link to an excellent video that explains why recoil does not occur until the projectile has left the barrel. Conservation of momentum is part of Newton's third law in a closed system it is not in contradiction to it.

PublicSafety400 is offline  
Old January 1st, 2017, 01:22 PM   #40
Scout Sniper
 
DudleyDR's Avatar
 
Join Date: Aug 2009
Location: Idaho
Posts: 784
Quote:
Originally Posted by PublicSafety400 View Post
Well, I'm willing to take the word of a physicist over the limited knowledge of all the M14 experts here. Here is a link to an excellent video that explains why recoil does not occur until the projectile has left the barrel. Conservation of momentum is part of Newton's third law in a closed system it is not in contradiction to it.
https://m.youtube.com/watch?v=1-s8NZ8xKW0

Take the time to read and digest this information from one of the M14 folks with limited knowledge. I was educated by one of the best Mechanical Engineering schools in the world at the time, Texas A&M University.

You want me to believe that a firearm has no recoil effect (it does not move rearward) until after the projectile has left the barrel and when any propellant gasses have been expelled and assume atmospheric pressure and there is no "opposite" force acting on the firearm? It is the expanding gasses from the propellant that provide the rearward momentum. That defies logic and common sense.

What your clown of a physicist does not take into account with his video - and since you agree - or at least profer (evidence offered in support of an argument) his video as proof, this may be a revelation to you as well. There are static physics and dynamic physics. There are theoretical physics and applied physics. Both of you have left out the acceleration factor variable of the velocity of the projectile. Your physicist calls his example a "snapshot" in the video. You are using a moment in time to justify your opinion as if the bullet stops so that you can calculate both momentums. The fact is that there is constantly increasing acceleration in the equation. From the time the cap is popped the bullet is accelerating - gaining momentum - until it leaves the barrel. Its KE (Kinetic Energy = 1/2 mass x velocity squared) is increasing from the time it starts moving until it stops exerting a negative linear force (rearward push) when it exits the barrel. Therefore recoil of the firearm starts (recall equal and opposite forces?) when the bullet starts moving. Recoil increases as the velocity of the bullet increases to match the momentum force developed by the bullet. This all happens before the bullet exits the barrel.

As a person with limited knowledge, I stand by my original statement.

Here is a short explanation from a student at the University of Alaska:

"The Physics Behind Guns
Although guns may not be everyday things for many of us, gun recoil is certainly something we're aware of (at least those of us that don't make Hollywood action films with guns whose recoil would instantly kill the person firing them!). Gun recoil is a result of momentum conservation, which is an extremely important fundamental principle. Newton was talking about momentum conservation when he wrote "every action has an equal and opposite reaction".
However, the physics behind all guns remain the same. Weapons such as cannons, shotguns and rifles, work on the basic idea of conservation of momentum and the change in energy from potential to kinetic.

Momentum characterizes an object's resistance to change in motion. If this is motion along a straight line, we call it linear momentum; if it is rotational motion we call it angular momentum. The basic idea is the same: moving things like to keep moving, and to change their motion we have to apply a force. If no force is present, then the momentum doesn't change, i.e. it is conserved.

Now, you might point out that a bullet coming out of a gun has a huge force on it from the exploding gunpowder. True enough, and that force is what propels the bullet forward. However, if you look at a bullet and gun together (say while the bullet is still in the barrel but already heading out at full speed), you can say there is no net force on the bullet-gun system. So the momentum of the bullet plus gun should be conserved.

If the bullet has mass mb and speed vb out of the gun, it has momentum pb given simply by
pb = mbvb
in the forward direction. To balance this momentum (and keep the net momentum of the bullet-gun system zero), the gun recoils with momentum in the opposite direction: pg = -pb, or
mgvg = -mbvb
Conservation of momentum is the law that is held true when the gun is fired and a "kick" is felt. When a bullet is fired from a gun, total momentum before is zero since nothing is moving. After firing the bullet there is a momentum in the forward direction. The gun must therefore have the same magnitude of momentum but in the opposite direction so that they cancel each other out leaving the total momentum still equal to zero. For this reason the gun must have a recoil velocity after the bullet is fired (i.e. the gun 'jumps' backwards and a 'kick' is felt).

As the bullet is propelled through the barrel, it gains momentum. In order for the entire system of the gun and the ammunition to have equal momentum, the gun must gain momentum in the opposite direction from the bullet. Momentum is a vector quantity, having both a direction and a velocity. The faster an object is moving or the more mass it has, the more momentum it has in the direction of its motion (momentum = mass velocity). Because momentum is a conserved quantity, it cannot be created or destroyed (momentum before = momentum after). It can only be transferred between objects. Momentum is conserved because of Newton's third law of motion.

When one object exerts a force on a second object for a certain amount of time, the second object exerts an equal but oppositely directed force on the first object for exactly the same amount of time. The momentum lost by the first object is exactly equal to the momentum gained by the second object. Momentum is transferred from the first object to the second object. In this case, if a gun exerts a force on a bullet when firing it forward then the bullet will exert an equal force in the opposite direction on the gun causing it to move backwards or recoil. Although the action and reaction forces are equal in size the effect on the gun and the bullet are not the same since the mass of the gun is far greater than the mass of the bullet. The acceleration of the bullet while moving along the gun barrel would be much greater than the acceleration of the gun (acceleration= force mass)."

Thanks from boomerpusher

Last edited by DudleyDR; January 1st, 2017 at 06:53 PM.
DudleyDR is offline  
Old January 1st, 2017, 02:08 PM   #41
Automatic Rifleman
 
Join Date: Sep 2016
Location: Texas
Posts: 131
Quote:
Originally Posted by DudleyDR View Post
Take the time to read and digest this information from one of the M14 folks with limited knowledge. I was educated by one of the best Mechanical Engineering schools in the world at the time, Texas A&M University.

You want me to believe that a firearm has no recoil effect (it does not move rearward) until after the projectile has left the barrel and when any propellant gasses have been expelled and assume atmospheric pressure and there is no "opposite" force acting on the firearm? It is the expanding gasses from the propellant that provide the rearward momentum. That defies logic and common sense.

What your clown of a physicist does not take into account with his video - and since you agree - or at least profer (evidence offered in support of an argument) his video as proof, this may be a revelation to you as well. There is static physics and dynamic physics. There is theoretical physics and there is applied physics. Both of you have left out the acceleration factor variable of the velocity of the projectile. Your physicist calls his example a "snapshot" in the video. You are using a moment in time to justify your opinion as if the bullet stops so that you can calculate both momentums. The fact is that there is constantly increasing acceleration in the equation. From the time the cap is popped the bullet is accelerating - gaining momentum - until it leaves the barrel. Its KE (Kinetic Energy = mass x velocity) is increasing from the time it starts moving until it stops exerting a negative linear force (rearward push) when it exits the barrel. Therefore recoil of the firearm starts (recall equal and opposite forces?) when the bullet starts moving. Recoil increases as the velocity of the bullet increases to match the momentum force developed by the bullet. This all happens before the bullet exits the barrel.

As a person with limited knowledge, I stand by my original statement.

Here is a short explanation from a student at the University of Alaska:

"The Physics Behind Guns
Although guns may not be everyday things for many of us, gun recoil is certainly something we're aware of (at least those of us that don't make Hollywood action films with guns whose recoil would instantly kill the person firing them!). Gun recoil is a result of momentum conservation, which is an extremely important fundamental principle. Newton was talking about momentum conservation when he wrote "every action has an equal and opposite reaction".
However, the physics behind all guns remain the same. Weapons such as cannons, shotguns and rifles, work on the basic idea of conservation of momentum and the change in energy from potential to kinetic.

Momentum characterizes an object's resistance to change in motion. If this is motion along a straight line, we call it linear momentum; if it is rotational motion we call it angular momentum. The basic idea is the same: moving things like to keep moving, and to change their motion we have to apply a force. If no force is present, then the momentum doesn't change, i.e. it is conserved.

Now, you might point out that a bullet coming out of a gun has a huge force on it from the exploding gunpowder. True enough, and that force is what propels the bullet forward. However, if you look at a bullet and gun together (say while the bullet is still in the barrel but already heading out at full speed), you can say there is no net force on the bullet-gun system. So the momentum of the bullet plus gun should be conserved.

If the bullet has mass mb and speed vb out of the gun, it has momentum pb given simply by
pb = mbvb
in the forward direction. To balance this momentum (and keep the net momentum of the bullet-gun system zero), the gun recoils with momentum in the opposite direction: pg = -pb, or
mgvg = -mbvb
Conservation of momentum is the law that is held true when the gun is fired and a "kick" is felt. When a bullet is fired from a gun, total momentum before is zero since nothing is moving. After firing the bullet there is a momentum in the forward direction. The gun must therefore have the same magnitude of momentum but in the opposite direction so that they cancel each other out leaving the total momentum still equal to zero. For this reason the gun must have a recoil velocity after the bullet is fired (i.e. the gun 'jumps' backwards and a 'kick' is felt).

As the bullet is propelled through the barrel, it gains momentum. In order for the entire system of the gun and the ammunition to have equal momentum, the gun must gain momentum in the opposite direction from the bullet. Momentum is a vector quantity, having both a direction and a velocity. The faster an object is moving or the more mass it has, the more momentum it has in the direction of its motion (momentum = mass velocity). Because momentum is a conserved quantity, it cannot be created or destroyed (momentum before = momentum after). It can only be transferred between objects. Momentum is conserved because of Newton's third law of motion.

When one object exerts a force on a second object for a certain amount of time, the second object exerts an equal but oppositely directed force on the first object for exactly the same amount of time. The momentum lost by the first object is exactly equal to the momentum gained by the second object. Momentum is transferred from the first object to the second object. In this case, if a gun exerts a force on a bullet when firing it forward then the bullet will exert an equal force in the opposite direction on the gun causing it to move backwards or recoil. Although the action and reaction forces are equal in size the effect on the gun and the bullet are not the same since the mass of the gun is far greater than the mass of the bullet. The acceleration of the bullet while moving along the gun barrel would be much greater than the acceleration of the gun (acceleration= force mass)."
You are free to believe what you want. I did my own research and came to this conclusion. I choose to only have to factor the speed of the projectile, and distance to determine where the bullet will land. If I have to consider every possible scenario of recoil then the computation would be impossible. With your position, each and every shot could result in a varying movement of the barrel due to recoil. If that were the case then there would hardly be a one MOA group to be found. Maybe you can perfectly control recoil through some mastered ability but I can't and never will.

Evidently you didn't listen to the video carefully. There is no recoil in a closed system because a change in momentum requires an external force acting on the system. There is no external force acting on a firearm until after the bullet leaves the barrel.

If the weapon begins to recoil before the bullet leaves the barrel that would mean the point you were aiming at has now changed because the weapon has now moved off the POA. Please don't tell me that sight adjustment incorporated recoil into the equation. That would be the first time that was heard!

Guess we will have to agree to disagree. Good luck!

Oh and here is a link to info about the "clown" of a professor as you put it.
https://en.m.wikipedia.org/wiki/Paul_G._Hewitt

PublicSafety400 is offline  
Old January 1st, 2017, 02:46 PM   #42
Scout Sniper
 
DudleyDR's Avatar
 
Join Date: Aug 2009
Location: Idaho
Posts: 784
Originally Posted by PublicSafety400 View Post
Well, I'm willing to take the word of a physicist over the limited knowledge of all the M14 experts here. Here is a link to an excellent video that explains why recoil does not occur until the projectile has left the barrel. Conservation of momentum is part of Newton's third law in a closed system it is not in contradiction to it.


A picture being worth 1000 words, I offer a moving diagram of an OPOC engine to help you understand my point. Observe how the expanding gasses exert momentum forces in equal and opposite directions while inside a cylinder. "Physics 101"

(upper illustration)

Now with that example in mind, imagine a cartridge case confined in a barrel just after firing when the projo is moving away from the cartridge case due to the expanding gasses between them. The piston on the left (the cartridge case / firearm combination) is moving away from the piston on the right (the projo). Now explain to me - if you can - how the force acting on the cartridge case in opposition to the ever increasing force developing and acting on the projo does NOT add up to recoil. Also, please explain how the firearm would start moving in the opposite direction of the projo when there are no high pressure gasses to act against it - after the projo "pressure containment plug" has left the barrel. Signed: Mr. Limited Knowledge (no expert)

Thanks from boomerpusher
DudleyDR is offline  
Old January 1st, 2017, 03:13 PM   #43
Scout Sniper
 
DudleyDR's Avatar
 
Join Date: Aug 2009
Location: Idaho
Posts: 784
PublicSafety400:

"If the weapon begins to recoil before the bullet leaves the barrel that would mean the point you were aiming at has now changed because the weapon has now moved off the POA. Please don't tell me that sight adjustment incorporated recoil into the equation. That would be the first time that was heard!"


DUH! Well, the point of aim has not changed, but the sight height design and the adjustment of the sights has taken recoil into consideration. Here is an easy example to see and understand. You obviously have no experience with a high-powered handgun like the Ruger single action .44 Magnum. Have you ever observed how tall the front sight is in relation to the rear sight? I think not. Have you ever looked at a picture of one? Even looking at a picture of one, if you use a straight edge (ruler) to align the top of the front sight with the top of the rear sight - a correct sight picture - you should notice that the centerline of the bore is pointing at a downward angle to a straight line of sight. That is because during the 7 1/2" that the bullet travels prior to its exiting the barrel, the muzzle end will rise to your original POA so that your bullet will hit what you aim at. Recoil raises the front sight arc so that the POI is not low. This is true of most firearms to varying degrees. There are many variables, but the principle is correct.

Maybe that is the first time that you have heard this or have taken it into consideration, but it is a "true fact"...not "fake news".

Thanks from boomerpusher

Last edited by DudleyDR; January 1st, 2017 at 03:37 PM.
DudleyDR is offline  
Old January 1st, 2017, 03:41 PM   #44
Lifer
 
2336USMC's Avatar
 
Join Date: Feb 2007
Location: The Road
Posts: 3,888
Well, I don't have a graduate degree in physics... but I did study physics for two years while studying mechanical engineering at one of the best engineering schools in the country (at the time), University of Minnesota Institute of Technology... as a National Merit Scholar. (DudleyDR and I can arm wrestle over it, but we would both have to bow to Massachusetts Institute of Technology. )

PublicSafety400, unfortunately what you quoted from the physicist says the exact opposite of what you are saying. The physicist clearly stated that the rifle is moving while the bullet is in the barrel. "closed system" means that the momentum of the bullet and the momentum of the rifle are equal.

Quote:
Originally Posted by PublicSafety400 View Post

This is a classic case in physics where linear momentum is conserved, with the result that the mass of the bullet times its forward speed is equal to the mass of the gun times its speed backward.
He just flat out said the rifle is moving. You misunderstood his explanation.

If not, then none of John Browning's recoil operated firearm designs would work.

If you have never shot a pistol, you might not be aware that you can change the POI of a pistol just by tightening your grip... because the pistol is recoiling while the bullet is still in the barrel. When someone complains that their pistol is shooting high, I can take it, put a firm grip on it and make it shoot right to POA, even 6" lower... just with grip pressure.

Rifle competitors are well aware that one of the fundamentals is using the exact same position and grip on the rifle for every shot, because a different grip, or moving the forward hand to a different spot on the foreend, or having the butt in a slightly different place in the shoulder pocket, can and WILL change the impact of the bullet. Because the rifle is recoiling, and we need for it to recoil as nearly the same as possible for every shot.

Quote:
Originally Posted by PublicSafety400 View Post
If the weapon begins to recoil before the bullet leaves the barrel that would mean the point you were aiming at has now changed because the weapon has now moved off the POA. Please don't tell me that sight adjustment incorporated recoil into the equation. That would be the first time that was heard!
Yes, that is EXACTLY what happens. And it's not the first time that was heard, it was the first time YOU heard it. Every target shooter knows this.

Quote:
Originally Posted by PublicSafety400 View Post
each and every shot could result in a varying movement of the barrel due to recoil. If that were the case then there would hardly be a one MOA group to be found.
Yes, that is EXACTLY what happens. The people who can get in position with a rifle, sling up, and shoot 1 MOA groups during a match have spent years learning how to do it, and are trying to explain it in this thread;.

Quote:
Originally Posted by PublicSafety400 View Post
Maybe you can perfectly control recoil through some mastered ability but I can't and never will.
Yes you can. By applying the basics as explained here and elsewhere, you could learn to do it. But apparently you won't. That's fine, it's your choice. It's actually hard work, and a person needs to be willing to accept coaching to get there.

Follow through and calling the shot are foundations upon which good groups and good scores are built. (There, see, I'm still on topic.)

Thanks from DudleyDR and boomerpusher
2336USMC is offline  
Old January 1st, 2017, 04:35 PM   #45
Automatic Rifleman
 
Join Date: Sep 2016
Location: Texas
Posts: 131
Ok here is a physicist that provides an explanation that will let all of us be right!
Accordingly by to him there is primary and secondary recoil. Primary recoil is barely noticeable. Secondary recoil is what we feel after the bullet exits the barrel!
Cheers!
http://www.bsharp.org/physics/recoil

Thanks from JEFFJP_N_JJ
PublicSafety400 is offline  
Reply

  M14 Forum > M14 M1A Forum > Accuracy

Moderator Tools
Display Modes




Top Gun Sites Top Sites List