budlight: Thank you for the advice. Your note and a couple of others show that those who are going to actually understand that the gun recoils due to the acceleration of the mass of bullet and combustion products from the moment of acceleration of the projectile mass are going to understand it. Those who can't are not. Great advice.
recoil v accuracy
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Buffalobob
Well-Known Member
Lightwind
RDM and Wildrose are nice guys who have a lot of good things to contribute to the forum. Wildrose kept his comments polite even when he disagreed and in case you don't know what it takes to get a Ranger tab, it takes an iron will and stubbornness. I do not take his stubbornness on this issue personally as it is obviously a very good trait to have when encountering adversity as a Ranger. We have been fighting two wars for a decade and you sure better have some stubborn people in uniform if you want to do that.
WildRose
Well-Known Member
Don't need to look it up. I'm quite familiar with both the 90 and 105 having fired both.
In both cases you are talking about a light weight, fairly portable weapons system that fires essentially a tank shell.
You are right the muzzle brake is at the back end and utilizes the propellant gasses to propel the weapon forward, instead of having them come out of the front end for the opposite effect.
I've also run the numbers, and the numbers tell me that with the mass of the rifle, mass of the projectile, force necessary to reach mv the reaward interial forces involved are minimum and not enough to affect accuracy; at least in the calibers we are talking about.
Even with the big guns you see no significant recoil effect until the round is exiting the barrel.
The recoil effect that does affect accuracy, is the human reaction to recoil.
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Where I work almost all of us are x-military because we require high security clearances. I imagine that this sight has a good % of x-military also. I am one of the few privileged enough to ware a national defense ribbon with a start (meaning Two war Vet) Vietnam and Desert Storm.
It's really just being born on the right year and have a career that covered both war time frames. Yes, and I can be a jerk and I don't like or trust the "other" branches of service.
It's really just being born on the right year and have a career that covered both war time frames. Yes, and I can be a jerk and I don't like or trust the "other" branches of service.
bman73
Well-Known Member
By no means am I a physics expert either, been 20 years since I even took it in school, but doesn't the fact that the bullet is moving down the barrel exclude it from being a closed loop system? It would seem to me that pressure on the back side of the bullet would be lower than that of the bolt face as it travels down the barrel or else the rifle would have to travel the same distance as the projectile? Not trying to raise anyones temper but it is an interesting discussion and I felt that I had a valid point to add to it.
Yes, having a bullet traveling down a barrel excludes it from being a closed system. You are correct.
As for the pressure being different on the bullet and the bolt face, the answer is no. It is a nearly isobaric system. What is happening is that the force on the rifle and the bullet is the same so they are moving proportionally to their mass. So, the bullet (and the hot gas) is accelerated faster by the ratio of the masses of the bullet (with combustion products) and the rifle.
As for the pressure being different on the bullet and the bolt face, the answer is no. It is a nearly isobaric system. What is happening is that the force on the rifle and the bullet is the same so they are moving proportionally to their mass. So, the bullet (and the hot gas) is accelerated faster by the ratio of the masses of the bullet (with combustion products) and the rifle.
SBruce
Well-Known Member
Perhaps what's needed to settle this once and for all, is slow speed film of a rifle on the bench, shooting free recoil, hair trigger.........and only the trigger is touched......couple of cameras from different angles but shown side/side on the screen.? One will see the trigger break and any resulting rear movement, while the other is showing the barrel crown and eventually the bullet release.......both cameras synched.....timer running......watching the whole shabang at once.?
Results would be easier to see if we shot a pretty heavy bullet quite slow, like under 2000'/sec I be thinkin.
I am still failing to understand how; If there is no rifle movement (other than shooter induced) untill the bullet is gone......then why do most top shooters in most fields say that consistant tracking/hold/stock pressure and return to battery do matter when it comes to shooting good groups.
Maybe I am just dense, but it seems that under the "no movement" theory; it wouldn't matter one darn bit how we hold the rifle or how consistant it reacts under recoil if the bullet is gone by time it does recoil.? Only thing that would matter is that the crosshairs are in the same place on target when the bullet leaves the rifle.
Most of the physics part of the discussion went right over my head, especially the closed vessel theories, so maybe I am just Dense.
Results would be easier to see if we shot a pretty heavy bullet quite slow, like under 2000'/sec I be thinkin.
I am still failing to understand how; If there is no rifle movement (other than shooter induced) untill the bullet is gone......then why do most top shooters in most fields say that consistant tracking/hold/stock pressure and return to battery do matter when it comes to shooting good groups.
Maybe I am just dense, but it seems that under the "no movement" theory; it wouldn't matter one darn bit how we hold the rifle or how consistant it reacts under recoil if the bullet is gone by time it does recoil.? Only thing that would matter is that the crosshairs are in the same place on target when the bullet leaves the rifle.
Most of the physics part of the discussion went right over my head, especially the closed vessel theories, so maybe I am just Dense.
SBruce: Don't worry about your view on this, it is absolutely correct. The rifle starts to move as soon as the bullet starts to move. The movement is due to the force on both of them. As you point out, the hold is important. That is why I am not sure about the amount of motion that was quoted in the article on triggers, but I am sure that the rifle starts to move immediately with the bullet (in the opposite direction of course). <G>
westcliffe01
Well-Known Member
Gentlemen, my first post here on this forum and apparently this is a controversial topic...
There is a nice description here of the mechanisms at work when firing a rifle, but as some have mentioned there are 2 separate things going on.
1) Forward motion of the bullet (Conservation of momentum)
2) Muzzle blast after the bullet has left the bore - action = reaction (can be reduced with a good quality muzzle brake)
It should be clear to anyone that the mass of the shooter and the way his body is arranged behind the weapon is a much larger factor than the mass of the weapon or the bullet. So the degree to which recoil is going to affect the shot has a lot to do with the "coupling" between shooter and weapon and how well "damped" this coupling is.
So, for obvious reasons, the prone position, with body aligned behind and almost on the same plane as the barrel is going to be favorable for absorbing recoil and is probably more conducive to a consistent shooting position and grip. Conversely, shooting from a standing position is probably the worst as far as controlling shot placement.
I personally have been having fits with trigger weight and overly short trigger over travel. It seems the vogue nowadays to reduce trigger over travel to a virtually imperceptible value as if it is something to brag about. However, when trigger pull weight is 3-4lb (9lb on my Remington from the factory !!) on a rifle which weighs 8lb, it does not take a genius to figure out that when the trigger breaks it still takes the striker a certain amount of time (around 3ms in the case of the Rem 700 LA) before it strikes the primer. If the trigger reaches the end of its travel sooner and transfers the trigger pull to the rifle itself, then the muzzle will move well before the bullet exits the barrel.
Thats my story and I'm sticking to it (heard that a lot lately ??)
There is a nice description here of the mechanisms at work when firing a rifle, but as some have mentioned there are 2 separate things going on.
1) Forward motion of the bullet (Conservation of momentum)
2) Muzzle blast after the bullet has left the bore - action = reaction (can be reduced with a good quality muzzle brake)
It should be clear to anyone that the mass of the shooter and the way his body is arranged behind the weapon is a much larger factor than the mass of the weapon or the bullet. So the degree to which recoil is going to affect the shot has a lot to do with the "coupling" between shooter and weapon and how well "damped" this coupling is.
So, for obvious reasons, the prone position, with body aligned behind and almost on the same plane as the barrel is going to be favorable for absorbing recoil and is probably more conducive to a consistent shooting position and grip. Conversely, shooting from a standing position is probably the worst as far as controlling shot placement.
I personally have been having fits with trigger weight and overly short trigger over travel. It seems the vogue nowadays to reduce trigger over travel to a virtually imperceptible value as if it is something to brag about. However, when trigger pull weight is 3-4lb (9lb on my Remington from the factory !!) on a rifle which weighs 8lb, it does not take a genius to figure out that when the trigger breaks it still takes the striker a certain amount of time (around 3ms in the case of the Rem 700 LA) before it strikes the primer. If the trigger reaches the end of its travel sooner and transfers the trigger pull to the rifle itself, then the muzzle will move well before the bullet exits the barrel.
Thats my story and I'm sticking to it (heard that a lot lately ??)
bigngreen
Well-Known Member
If all recoil was from gasses exiting the barrel wouldn't every bullet weight recoil the same given the same powder charge. All the recoil calculations I've ever seen needs bullet weight. The Physics of Everyday Stuff - Gun Recoil
WildRose
Well-Known Member
The amount of gasses expended which force the rifle backward are directly related to the pressures attained. With the same powder and a heavier bullett you will generate more pressure to expel it.
WildRose
Well-Known Member
If you have a strong spring, and a fast firing pin coupled with a light trigger that breaks crisply and cleanly with zero over travel you have the best of all worlds.
The problem with lots of over travel is that when the trigger breaks and the firing process begins, is that your finger is going to accelerate a good bit before hitting the trigger stop. That makes you very prone to jerking to such an extent it will affect accuracy.
Personally on all my rifles I prefer about a 1.5lbs pull and zero over travel or as little as is possible. That way I have the best of all worlds.
I buy that you have two types of recoil as has been discussed, the primary recoil that occurs while the bullet is in the barrel can effect impact of the bullet depending on whether this energy causes movement of the barrel whether it's harmonics or recoil. For practical purposes who cares. I think we are trying to shoot more accurately in the end.
Bench rest guys shooting sub half inch groups at 300 yards know this quite well. They deal with it with light recoil calibers, very heavy rifle mass, and very sophisticated rifle rests complete with talcom powder on the contact surfaces to make sure the rifle moves back at firing as perfectly straight as possible with no body contact with the rifle except for the 2 oz trigger. If the bullet was gone before ignition they would have found this out long ago and saved a ton of money.
The primary movement may not be noticed in many cases because other factors overcome the effect. Your talking thousandths of an inch that can't be seen in ithe videos shown in previous posts.....you could likely see it with slow speed photography at magnification.
Bench rest guys shooting sub half inch groups at 300 yards know this quite well. They deal with it with light recoil calibers, very heavy rifle mass, and very sophisticated rifle rests complete with talcom powder on the contact surfaces to make sure the rifle moves back at firing as perfectly straight as possible with no body contact with the rifle except for the 2 oz trigger. If the bullet was gone before ignition they would have found this out long ago and saved a ton of money.
The primary movement may not be noticed in many cases because other factors overcome the effect. Your talking thousandths of an inch that can't be seen in ithe videos shown in previous posts.....you could likely see it with slow speed photography at magnification.
bigngreen
Well-Known Member
But we keep the pressure the same or close as we can and we use less powder with the heavier bullet, which translates into less propellent at the end of the muzzle but if we go from a 225gr bullet to a 300gr bullet the recoil difference is significantly increased with a lighter charge of powder at the same pressures.
