No...
Tight hold vs velocity
- Thread starter rmist
- Start date
No...
I'm glad someone else has brought this up!
I'm one of the people who have tested this and it is real. My testing has been limited to 13.5lb guns in a couple of different typical BR cartridges. I've been preaching about this to a few people when discussing tune and what affects it. Obviously, this is only a part of the equation to good tune but the chrono doesn't lie...at least not in this context, as actual speed isn't as important as comparative speeds for this test.
The whole notion behind my thoughts on it are related to the fact that I've probably got as much or more experience testing tuners and doing vibration analysis than anyone I know of, as I build and sell tuners that have been tested by using electronic equipment to measure frequency, amplitude and time, as well as the real proving ground...at matches against other good shooters and equipment.
That said, I've not done testing specific to the subject of this thread, other than chrono testing. With the guns, rests, and calibers that I've tested, about 30-40fps difference in velocity between pinned hard against the rest stop and free recoiling the rifle, was pretty consistent at all times. There's a lot of little things that can come into play too, like how much does the gun weigh, how slick are the bags, how tight in the front rest, what caliber, and even if shooting uphill or downhill makes some difference.
As others have alluded to already, there really is a consistent and repeatable velocity difference pinned hard vs. free recoil. That's where my tuner testing comes into play. This post could be a very long one if I attempt to get into all of what I've found to be factual via testing regarding tuners, but suffice it to say that tuners work by changing the frequency that the barrel vibrates at, ideally timing bullet exit with the muzzle pointing at the same place from shot to shot. 30-40fps isn't a lot, but consider this...how can it be physically possible for the barrel muzzle to be exactly at the same place in it's vibrational movement with two different velocities...period? Not to mention that the vibrational frequency and amplitude are also affected by how much energy is allowed to dissipate by a gun that breaks away freely in the bags vs one that is very rigid. Someone else mentioned about the time that the bullet is in the barrel vs how far the gun moves in the same amount of time. It's small. I've read that it was calculated to be about .050" but don't recall rimfire or centerfire...but it's roughly calculable either way and that doesn't really matter as to whether or not this is real..as any difference can make a difference. Others have tested guns with the barrel literally in poured concrete. The results were not goo, IIRC, but nevertheless, a gun that is mounted rigidly will vibrate differently and produce higher velocity than one that is not. That, IMO, is not debatable but rather, plain ol physics.
Anyway, I'm very convinced, no matter how big or small the difference is, it does make a difference. There's physically no way other than blind luck to be in 100% perfect tune if the velocity and vibrational frequency and amplitude are different due to different velocity and energy absorption or lack of. In the last short while ther has been a widespread acceptance that tuners can and do make a big difference with as little as .001" of tuner travel. If that is true...and it is, why would we accept that the tune is perfect with 30-40fps difference in velocity and different harmonics from being pinned or free recoiled?
I won't argue with anyone that says it needs more testing. To that, I agree and say have at it, if you have good equipment and means of helping to provide conclusive and definitive results. In the meantime, I have enough information to satisfy myself in that it's worth looking into. It simply a logical conclusion to assume that a gun that fires rounds at different speeds and at different recoil rates and thus energy dissipation will not and can not be in perfect tune in both states.----Mike Ezell
I'm one of the people who have tested this and it is real. My testing has been limited to 13.5lb guns in a couple of different typical BR cartridges. I've been preaching about this to a few people when discussing tune and what affects it. Obviously, this is only a part of the equation to good tune but the chrono doesn't lie...at least not in this context, as actual speed isn't as important as comparative speeds for this test.
The whole notion behind my thoughts on it are related to the fact that I've probably got as much or more experience testing tuners and doing vibration analysis than anyone I know of, as I build and sell tuners that have been tested by using electronic equipment to measure frequency, amplitude and time, as well as the real proving ground...at matches against other good shooters and equipment.
That said, I've not done testing specific to the subject of this thread, other than chrono testing. With the guns, rests, and calibers that I've tested, about 30-40fps difference in velocity between pinned hard against the rest stop and free recoiling the rifle, was pretty consistent at all times. There's a lot of little things that can come into play too, like how much does the gun weigh, how slick are the bags, how tight in the front rest, what caliber, and even if shooting uphill or downhill makes some difference.
As others have alluded to already, there really is a consistent and repeatable velocity difference pinned hard vs. free recoil. That's where my tuner testing comes into play. This post could be a very long one if I attempt to get into all of what I've found to be factual via testing regarding tuners, but suffice it to say that tuners work by changing the frequency that the barrel vibrates at, ideally timing bullet exit with the muzzle pointing at the same place from shot to shot. 30-40fps isn't a lot, but consider this...how can it be physically possible for the barrel muzzle to be exactly at the same place in it's vibrational movement with two different velocities...period? Not to mention that the vibrational frequency and amplitude are also affected by how much energy is allowed to dissipate by a gun that breaks away freely in the bags vs one that is very rigid. Someone else mentioned about the time that the bullet is in the barrel vs how far the gun moves in the same amount of time. It's small. I've read that it was calculated to be about .050" but don't recall rimfire or centerfire...but it's roughly calculable either way and that doesn't really matter as to whether or not this is real..as any difference can make a difference. Others have tested guns with the barrel literally in poured concrete. The results were not goo, IIRC, but nevertheless, a gun that is mounted rigidly will vibrate differently and produce higher velocity than one that is not. That, IMO, is not debatable but rather, plain ol physics.
Anyway, I'm very convinced, no matter how big or small the difference is, it does make a difference. There's physically no way other than blind luck to be in 100% perfect tune if the velocity and vibrational frequency and amplitude are different due to different velocity and energy absorption or lack of. In the last short while ther has been a widespread acceptance that tuners can and do make a big difference with as little as .001" of tuner travel. If that is true...and it is, why would we accept that the tune is perfect with 30-40fps difference in velocity and different harmonics from being pinned or free recoiled?
I won't argue with anyone that says it needs more testing. To that, I agree and say have at it, if you have good equipment and means of helping to provide conclusive and definitive results. In the meantime, I have enough information to satisfy myself in that it's worth looking into. It simply a logical conclusion to assume that a gun that fires rounds at different speeds and at different recoil rates and thus energy dissipation will not and can not be in perfect tune in both states.----Mike Ezell
BoydAllen
Gold $$ Contributor
We all would like to shoot better. The point of the story was to encourage trying a lot of different ways to shoot a given rifle. My bench rifle, on a easy day, with its best barrels, has put me into the mid ones (five shot groups), measured with the same tool used at short range matches. I will never take the time and money that it takes to be an accomplished short range competitor, but I know the game pretty well, and have watched record holders shoot on many occasions. As I wrote, many shooters go about what they are trying to do in a manner that is doomed from the outset, and instead of trying different methods, and equipment, just keep doing the same experiment, over and over, hoping for different results.
I agree with the Phooey on bogus science part. Unfortunately your "science" is ............... um.... well, let's say not actual science.
Sometimes it helps to take things to the limit to help understanding. Impulse is force x time or Mass x change in velocity (which is the same as change in momentum).
Imagine a rifle with a mass of 69 grains (including the case weight) firing a bullet which weighs 69 grains. Suspended by a string, when the charge ignited the bullet would fly out of the cartridge one direction at a high velocity and the rifle would recoil the other direction with the same velocity; i.e. the change in momentum would be equal and opposite.
But if the lightweight rifle were restrained so that it could not move, then the change in momentum of the rifle would be zero and the entire impulse would be dedicated to launching the bullet, this time at a higher velocity.
Of course a real rifle has much more mass than 69gr (let's not argue mass vs weight in this thread please) but the idea is the same. Energy from the charge can be entirely dedicated to launching the bullet (can we also ignore noise and light please?) or it can be partially dedicated to moving the rifle the opposite direction, depending on how the rifle is restrained.
Not really - you cannot restrain a 10 pound rifle from moving rearward 0.006" - and if you did, PLEASE tell me how much more velocity you gain with a 0.006" longer barrel.
The original question was free recoil vs held against the shoulder... and you are arguing angels and pinheads - a silly case, and a total waste of time.
So, are you saying that you have shot both ways, over a chronograph and saw no difference in velocity?
Yup... and if there is a theoretical difference, it is smaller than the ES and lost in the noise.
BoydAllen
Gold $$ Contributor
I once read an article that had data that supported the idea that differences in hold can produce differences in velocity. It has been too long for me to remember the source, but I do remember that. I would think that this would be the most extreme shooting a heavy bullet in front of a large cartridge in a light rifle, and much less if those specifications were the opposite.
Well, I'm saying that I have too and that it did make a difference. Only one of us is right or it matters more in some setups than others. I've already described the equipment I used, which is typical br equipment and calibers.
Thanks all I thought internal pressure is why you get the speed Now I know different tonight when we race I will add more weight to the oil pan so the cylinders make more pressure . Larry
Only thing I have done is changed the stocks. They have 11 pound difference the speed was the same . Larry
skiutah02
Silver $$ Contributor
I'm willing to bet that if you filled the oil pan so high that the pistons couldn't move in response to the fuel detonation you would see an increase in your engine's combustion chamber pressure.
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Please allow me a shot at this debate: Relative mass, or weight at we call it on earth, behaves in proportion to it's velocity.
Most folks may never understand that principle, but I share this tidbit for the few that are smarter then a box of rocks.
Foot pounds of energy are squared each time you double the velocity. Do the math to see how you can apply the inertia factor.
Shoot the primer on a slug shell with a BB gun and see the case hit you between the eyes!
Mr. Wizard says Hi!
Most folks may never understand that principle, but I share this tidbit for the few that are smarter then a box of rocks.
Foot pounds of energy are squared each time you double the velocity. Do the math to see how you can apply the inertia factor.
Shoot the primer on a slug shell with a BB gun and see the case hit you between the eyes!
Mr. Wizard says Hi!
I never have filled the Chamber from the oil pan . I will leave that trick to you. Larry
skiutah02
Silver $$ Contributor
Edited my post for clarity.
hpshooter
Gold $$ Contributor
"Shoot the primer on a slug shell with a BB gun and see the case hit you between the eyes!"
Darn, I thought my cousin and I were the only two 7 year olds on earth that were dumb enough to try that.
As an aside, I would bet that more than a few on this site have "cured" a newbies failure to feed in a 1911 by having them tighten their grip so the energy that is making the gun bounce around in their hand is now driving the slide back all the way. (We used to call it "limp wristing" . Guess a new term will have to be coined to be PC.)
Darn, I thought my cousin and I were the only two 7 year olds on earth that were dumb enough to try that.
As an aside, I would bet that more than a few on this site have "cured" a newbies failure to feed in a 1911 by having them tighten their grip so the energy that is making the gun bounce around in their hand is now driving the slide back all the way. (We used to call it "limp wristing" . Guess a new term will have to be coined to be PC.)
Spot on! Way back when I used a 45 ACP to compete I would often load very light and noticed that when my wife would often cause a stove pipe round and wondered why.
After I realized that she did not hold her grip as tight as me and that caused the problem.
Interesting that you brought that point to mind.
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