recoil v accuracy

[WildRose]

WildRose: Please excuse my nit-picking but I am still not completely understanding a couple of your answers. Some of them are very close to my view and I am ready to agree to some of those. However, there are still some issues you brought up I don't fully understand.

A) You said (on page 13): "Incorrect, pressure continues to build as long as it is constrained by the bullett and it is still burning."

What I interpret "pressure continues to build" to mean is a monotonically increasing curve of pressure.

Your interpretation, not my intent.

As the volume increases the pressure drops from the initial. However. With a faster burning powder, combustion is completed very quickly. That is why we use the faster burning powders with lower volume cases, and shorter bbls with the fastest burning powders typically being used in pistol cartridges.

With our larger caliber, higher capacity cases and heavier projectiles we utilize slower burning powders in order to spread out the total time pressue is being created through combustion.

If all the powder is consumed inside the case/chamber, your highest velocity potential comes when the bullet separates from the case.

What we do instead with the slower burning powders and longer barrels is to continue combustion throughout the length of the barrel, so that while the pressure gradient falls as the case/bullet separates, we have a longer burn time allowing for more total velocity.

Same exact load fired in shorter vs longer barrels provides consistenly higher velocities for that reason. You have a longer time for burn and thus increased velocity.

Your qualification of the sentence was: "as long as it is constrained by the bullett and it is still burning." I take that to mean if you have a long burning powder that can still have particles burning as they leave the barrel the pressure would increase until the projectile leaves the barrel. That is very different from another statement of Roberto:

No you continue producing pressure, but the peak pressure is reached in the first milisecond. Pressure begins to drop as the volume increases, but it continues pushing longer, and producing ever greater velocity the longer that pressure is constrained in the pressure vessel of the chamber and bore. Longer burn time, more total volume of gas produced, more total velocity with lower pressures than would be produced by a faster burning powder.

This statement is quite confusing. If pressure is continuing to build as long as you have combustion of the powder, that would mean it was increasing (building). However, in the next sentence you say: "Yes the pressure itself peaks when the bullet separates from the case." It can't be both. Either it peaks at the case or it peaks at the point where combustion stops. Which is is? Do you see why this confuses me?

The pressure peak, is not the end of pressure being produced.

Let me address the point about powder needing to be burning for the bullet to be accelerating: " If all the powder were consumed at the point of maximum pressure in the chamber, maximum velocity would be reached there and continue to drop as the round travels down the bbl." Let me explain why that is wrong. At every point in the barrel the pressure behind the bullet is greater than atmospheric pressure. The forces holding the bullet back in its acceleration are friction and atmospheric pressure. As long as the pressure from the rear of the bullet is larger than the pressure in front of the bullet by enough to to overcome friction the bullet will continue to accelerate (although at a lower rate). Consequently, as long as the pressure behind the bullet is substantially greater (and decreasing from the peak behind it) than the pressure in front the bullet will go faster, not slow down just because it is in front of the pressure peak regardless of powder burning or not. Do you see this point - or do we still disagree on this one?

The bullet cannot accelerate faster than the gas behind it expands. When the pressure peaks, if combustion does not contine as the volume of the cylinder increases, velosity would necessarily be retarded and the friction produced between the bullet and lans/grooves would quickly decelerate it.

We are not acting in the absence of friction here and by necessity the friction is considerable in order to achieve the desired pressures for acceleration.

Only through the continued release of those hot gases produced by the combustion, can the projectile contine to gain speed rather than lose it.

I am going to hit the sack but I am enjoying the conversation. Your positions have forced me to do something I have wanted to do for a while and that is to apply science to shooting. I even picked up a good ballistics book that it looks like will take me a year to get through. I am sure you will have some of your own points and I look forward to them.

One of the best reads ever on the subject.

Hornady 99238 Handbook of Cartridge Reloading 8th Edition#

Of course I'm still working off of the 2nd edition.

 

[justgoto]

I'm with WildRose on this issue. I've argued this issue on 2 other sites; (you know your days are numbered when the mod starts the ridicule.) No one could get passed ridicule, while copying and pasting Newtons Law.

I'm glad this site is here; the only firearm forum I know of, where people debate issues politely. Makes for great reading, learning and argument formulating.

 

[WildRose]

I'm with WildRose on this issue. I've argued this issue on 2 other sites; (you know your days are numbered when the mod starts the ridicule.) No one could get passed ridicule, while copying and pasting Newtons Law.

I'm glad this site is here; the only firearm forum I know of, where people debate issues politely. Makes for great reading, learning and argument formulating.

I have a rule with moderators. As soon as they get personal and insulting they can kiss my hairy hindparts goodbye.

Scroll back through the posts to the link on the recoil sled experiments and you'll see what I mean.

If a muzzle brake can reduce felt recoil by over 65%, then indeed it is not the recoil but how we react to it or in anticipation of it that has the most significant impact on accuracy/precision.

By the time the inertial forces have caused any significant movement of the weapon, the round is out of the chamber.

If this were not the case, we would not be able to hit a house with a 155mm artillery shell from 11 miles away. We can, in fact with the new faster guns we can put three shots in the same hole (within 25m) in less than 3 seconds by varying the charge and elevation.gun)

[ame="http://www.youtube.com/watch?v=h-nnUiMgE24&feature=player_detailpage"]Future Weapons : PzH 2000 English long version - YouTube[/ame]

 

[westcliffe01]

Do you think you can discern something that happens in half a millisecond ? I think what is missing in the force measurement is that if the X axis were extended several times longer than shown, then the muzzle blast would appear. You will notice they say the bullet leaves the barrel right at 1ms. The muzzle blast may extend out to 3, 5 or 10ms.

The bullet reaches the end of its acceleration no later than the end of the barrel and quite possibly (in a long barrel) slightly before the end of the barrel, particularly if not working with max loads (very typically the case for accuracy vs max downrange energy). So it would be logical that the impulse from accelerating the bullet reach a zero value before or at the point it reaches the muzzle.

I guess we could ask varmint Al if he had the additional data beyond the 1ms point. So far I have not gotten him to answer emails, and given his age it is hard to say how active he is with the website.

 

[Buffalobob]

I've argued this issue on 2 other sites; (you know your days are numbered when the mod starts the ridicule.) No one could get passed ridicule, while copying and pasting Newtons Law.

Ridicule is all it deserves. We are being polite to Wildrose but what he has posted is simply utter nonsense bolstered by bugs bunny type cartoons from youtube.

The laws of motion formulated by Newton must be obeyed, first and foremost. When one has to invoke magic pixie dust by claiming a delta T delay in conservation of momentum it becomes apparent that one has no regard for science and is only passing off opinion and that one believes if one posts the same incorrect and unfounded opinion enough times that it will be come true.

What it takes to get a degree in physics is 36 semester hours of physic and 21 semester hours of math of which 6 must be more advanced than theoretical differential equations. The drop out rate of students in my physics classes was very similar to the drop out rate in my special forces training. About the same percentage actually graduate.

There are as far as understand it three of us degreed physicists telling Wildrose as politely as we can that what he has posted is ludicrous ******** and the more he repeats it the stupider it gets.

 

[WildRose]

Ridicule is all it deserves. We are being polite to Wildrose but what he has posted is simply utter nonsense bolstered by bugs bunny type cartoons from youtube.

The laws of motion formulated by Newton must be obeyed, first and foremost. When one has to invoke magic pixie dust by claiming a delta T delay in conservation of momentum it becomes apparent that one has no regard for science and is only passing off opinion and that one believes if one posts the same incorrect and unfounded opinion enough times that it will be come true.

What it takes to get a degree in physics is 36 semester hours of physic and 21 semester hours of math of which 6 must be more advanced than theoretical differential equations. The drop out rate of students in my physics classes was very similar to the drop out rate in my special forces training. About the same percentage actually graduate.

There are as far as understand it three of us degreed physicists telling Wildrose as politely as we can that what he has posted is ludicrous ******** and the more he repeats it the stupider it gets.

One thing that is sad is that some engineers have spent so much time in the lab they failed to learn through observation of experiments.

If engineers and physicists always had it right, we wouldn't kill people with collapsing bridges and buildings, or airplanes that fly only on paper.

What I have stated is 100% factual, and proven through experiments like the recoil sled experiment.

It is also proven daily by those that fire heavy magnums with and without muzzle brakes.

You pontificate and blow steam, but I actually produced the numbers to plug into the formulas and they do not support the claim that inertia alone is the primary force involved in felt recoil.

You cannot get a recoil reduction of over 65% by installing a good muzzle brake if the thrust from the muzzle blast is not the primary driver.

If a projectile traveling down the barrel is running at an average speed of 1500fps in an average sporter bbl of 24" that bullet has cleared the barrel in .00133 seconds.

With an average recoil speed of 14fps the maximum possible movement of the rifle due to inertial forces alone is .0162 feet prior to the bullet exiting the barrel.

That is NOT enough to affect accuracy to any significant degree if you are holding on to the rifle at all.

Rifle Recoil Table

 

[WildRose]

I'm with WildRose on this issue. I've argued this issue on 2 other sites; (you know your days are numbered when the mod starts the ridicule.) No one could get passed ridicule, while copying and pasting Newtons Law.

I'm glad this site is here; the only firearm forum I know of, where people debate issues politely. Makes for great reading, learning and argument formulating.

It was nice while it lasted.

 

[Buffalobob]

You pontificate and blow steam, but I actually produced the numbers to plug into the formulas and they do not support the claim that inertia alone is the primary force involved in felt recoil.

Inertia is not a force. lightbulb If you wish to run a line of ******** on people you should at least look up the terms you use so you know their meaning.

 

[lightwind]

WildRose:

Good job of crunching numbers. You said: "With an average recoil speed of 14fps the maximum possible movement of the rifle due to inertial forces alone is .0162 feet prior to the bullet exiting the barrel." That would be about .19" using averages instead of integrals and for a fast bullet. If you recall the article by Darrell Holland on Dwell time:

Dwell Time And Your Trigger

He stated that: " This critical time is around .025 thousands of a second and the rifle will recoil rearward approximately .250 -.375 inches before the bullet exits the barrel. Variables being the weight of the rifle, muzzle velocity and bullet weight." And he used the more complex approach of integration and actual measurement. However, your number is close to his and that is very good approximation. The point is that if the whole rifle has moved about 0.2" that is significant. It is also why hold and follow through are so important so that the rifle is moving directly back during this initial excursion. If it twists or yaws the barrel will be pointing the projectile in the wrong direction.

As you said: "That is NOT enough to affect accuracy to any significant degree if you are holding on to the rifle at all."

However, I would substitute "correctly" for "at all." The reason I say that is that you have learned to hold the rifle "correctly." Your training is such that if you are holding the rifle "at all" you are holding it correctly. That is not the same for all of us who are shooting. That is the reason that I am sure you will shoot much better than I but that does not necessarily mean that what you do will translate directly to the physics of shooting. It is the way you were trained without all of the details of why. For you, 0.20" travel is not bad. For some, that 0.20" will be translated into barrel motion and twist. You shoot well because of training. We don't all have that training built in to our DNA so we have to learn to shoot like you do and some of us have to do that by recognizing why.

 

[WildRose]

Inertia is not a force. lightbulb If you wish to run a line of ******** on people you should at least look up the terms you use so you know their meaning.

I may not be eloquent in geek speak but my numbers are correct, and you have not presented any contrary evidence which would dispute them

The experiemtal evidence I provided supports my contentions 100% and you can provide nothing that shows otherwise.

Now stuff the snark and act like an adult.

 

[WildRose]

WildRose:

Good job of crunching numbers. You said: "With an average recoil speed of 14fps the maximum possible movement of the rifle due to inertial forces alone is .0162 feet prior to the bullet exiting the barrel." That would be about .19" using averages instead of integrals and for a fast bullet. If you recall the article by Darrell Holland on Dwell time:

Dwell Time And Your Trigger

He stated that: " This critical time is around .025 thousands of a second and the rifle will recoil rearward approximately .250 -.375 inches before the bullet exits the barrel. Variables being the weight of the rifle, muzzle velocity and bullet weight." And he used the more complex approach of integration and actual measurement. However, your number is close to his and that is very good approximation. The point is that if the whole rifle has moved about 0.2" that is significant. It is also why hold and follow through are so important so that the rifle is moving directly back during this initial excursion. If it twists or yaws the barrel will be pointing the projectile in the wrong direction.

As you said: "That is NOT enough to affect accuracy to any significant degree if you are holding on to the rifle at all."

However, I would substitute "correctly" for "at all." The reason I say that is that you have learned to hold the rifle "correctly." Your training is such that if you are holding the rifle "at all" you are holding it correctly. That is not the same for all of us who are shooting. That is the reason that I am sure you will shoot much better than I but that does not necessarily mean that what you do will translate directly to the physics of shooting. It is the way you were trained without all of the details of why. For you, 0.20" travel is not bad. For some, that 0.20" will be translated into barrel motion and twist. You shoot well because of training. We don't all have that training built in to our DNA so we have to learn to shoot like you do and some of us have to do that by recognizing why.

That is a much more critical point in time actually. Any movement before the strike of the of the primer can pull you off target.

It can also initiate momentum either rearward, at an angle, or in a twisting fashion. Get that movement started, then add the force of the recoil and your errors can compound exponentially.

If you are on target at the strike of the primer, the only thing you have to deal with is whatever minimal amount of movement that is going to go on in the next .0013 seconds or less.

Think of a car that is traveling down the road at 30mph who is suddenly struck in the rear by a car traveling 45mph... . Sum of all forces. It will accelerate you forward in a direct line with the force of impact, but unless he's hitting you from an angle it is not going to deviate you from your line of travel to any significant degree.

Also you have to consider that when in a shooting position, the primary direction of travel for any force of recoil is going to be in a straight line through the bore of the rifle and beyond. That doesn't allow for much variation in your actual target alignment, it just moves you .02 inches farther away from your target.

Yes muzzle flip can be a factor at that point, but again with rifles it is not the primary problem we deal with just because of the axis involved.

With pistols the muzzle flip is a much greater problem just because of the lever effect involved with how we hold one.

As for the highlighted, I appreciate but but it may well not be the case. I can guarantee you however I can probably in short order teach you to shoot better than you currently think you can.

As for the hold factor. I have done experiments just to gauge recoil before letting kids shoot different weapons.

Great example here.

My 8yo niece wanted to shoot my 7 mag. At the time she weighed around 55lbs (Very petite girl). It had the boss muzzle break and I thought, "Well it doesn't bother me at all but how bad is it really, and how bad would it be for a child that weighs just over 1/4 of my weight.

I set up the target, set it on a bipod, rested the butt on sand bags. Put it on target at 100yds, and hit the 1" Bull of the target.

I repeated this for three shots in about a 2 minute period. So it held MOA even without any "stop" for the end of the butt.

This was a basically factory model 70, at around 7lbs. The rise off of the bipod was about 1.5" and the rearward travel was under one inch. My only hold was with my hand on the pistol grip.

An hour later I had my neice hitting paper plates at 300yds.

 

[WildRose]

.... .

 

[westcliffe01]

WildRose, your contempt for engineers certainly shows in your writing. Like all fields, many of those participating are mediocre. Many are average, who mainly follow orders. The mediocre ones struggle to do even that. Some are morons. And some are brilliant. Artisans, in particular, who are frequently called upon to create what the engineer has dreamed up, thought out, planned or thrown together have the least respect - often deservedly so. What I learned a long time ago is that the toughest respect to earn is from the artisans. Once they are on our side you can accomplish anything. But the introduction is always tough and one is always assumed to be and treated like an idiot to begin with..

The education system here in the US is part of the reason for the downfall of our engineering excellence. It seems this is the only country in the world where a nurse taking her bachelors year can get by without taking a single biological or scientific subject. My wife (who is a nurse) had to take a religion class, a psychology class and an "art" class in her bachelors year. She took a class in photography (cost over $1000) and they didn't teach the participants the most basic shutter speed / aperture / depth of field theory.

I would like to know what it would take for you to accept that recoil begins at the moment of ignition ? A plot of force on the rifle butt vs pressure in the chamber ? I am thinking that a Mosin Nagant is only $80 and I have access to measurement equipment. I couldn't measure pressure directly, but I could strain gauge a cylindrical part of the barrel, maybe just after the action (one wants an area where the stress will be uniform). Strain gauges are relatively cheap and one could fit 4 around the circumference of the barrel and average the signals, in case any funky bending is taking place. And I am sure I can borrow a load cell to fix to the butt.

I don't think I will measure anything on the fore end, since most of us know that the barrel is not directly in line with the butt, which is why the muzzle climbs under recoil in the first place. Perhaps just strap it down with 2 ratchet straps so that it can neither lift, nor move laterally. if these are angles back a little, one could put some preload on the butt and the loadcell could engage in a socket so that the but can neither move up, down or sideways.

How does that sound ? If the facts do not emerge the way you have claimed, how will you react ? Will we see some repentance ?

Because if the facts go the other way they will be getting shown too.

The Nagant appeals to me for this experiment, since it has a pretty good recoil, shooting a fairly heavy bullet.

One thing that is sad is that some engineers have spent so much time in the lab they failed to learn through observation of experiments.

If engineers and physicists always had it right, we wouldn't kill people with collapsing bridges and buildings, or airplanes that fly only on paper.

 

[WildRose]

WildRose, your contempt for engineers certainly shows in your writing.

You couldn't be more wrong. The man I most admired and respected in my entire life was an engineer, what little good their is in me came from he and my other grandfather. He also blessed me with endless lessons on how to explain life through basic physics.

I just can't stand rude, arrogant, condescending jackasses, something which tends to run rampant in many professions, not just engineering.

I would like to know what it would take for you to accept that recoil begins at the moment of ignition ? A plot of force on the rifle butt vs pressure in the chamber ? I am thinking that a Mosin Nagant is only $80 and I have access to measurement equipment. I couldn't measure pressure directly, but I could strain gauge a cylindrical part of the barrel, maybe just after the action (one wants an area where the stress will be uniform). Strain gauges are relatively cheap and one could fit 4 around the circumference of the barrel and average the signals, in case any funky bending is taking place. And I am sure I can borrow a load cell to fix to the butt.

I accept that it begins with ignition. I dont' accept that it is significant to accuracy.

I have proven beyond a shadow that the bulk of measurable and felt recoil is due to muzzle blast, which of course occurs as the round exits along with the burning propellant.

I don't think I will measure anything on the fore end, since most of us know that the barrel is not directly in line with the butt, which is why the muzzle climbs under recoil in the first place.

Which is not enough to affect accuracy to a significant degree. We've already gone over the numbers.

How does that sound ? If the facts do not emerge the way you have claimed, how will you react ? Will we see some repentance ?

My own expriment and the recoil sled expriment I linked to are more than adequate to prove my point.

Because if the facts go the other way they will be getting shown too.

They won't.

I sincerely wish I had access to some super high speed video equipment. I thought up an experiment using a rifle supsended by wires at each end being fired, with a thin wire also being used to mark the leading edge of the muzzle so we could measure rearward travel and muzzle flip prior to the expulsion of the round.

Do one set of measurments with and another without a good muzzle brake attached, and measure the difference in the two.

No need for high tech, just a ruler and known points of reference with visual evidence is quite adequate.

The Nagant appeals to me for this experiment, since it has a pretty good recoil, shooting a fairly heavy bullet.

My limited exerience with the Nagant is that they buck like a mule. It's also all but impossible to find one that hasn't been shot to hell with major issues in throat erosion and riflings being rather smoothed.