Closed v. Open (Bolt)

[hitech]

Originally posted by pbjosh
Alot of people have taken the easy way out and said "all the guns firing at the same velocity shoot the same distance" but don't think that is right. Look at the Flatline barrels. That alone breaks the statement all to bits...
Saying the range is totally a factor of velocity puts you in the "Earth is Flat" group.

I think what "most" of us say/mean is that without spin, guns firing at the same velocity shoot the same distance. Sometimes we just get lazy and leave out the "without spin" part. As far as I know, NO ONE has EVER proven that anything other than spin (and velocity) affect distance and accuracy of a standard paintball.

[Paladin]

[QUOTE]Your gun isn't accurate. It's accurate enough.

Originally posted by SlartyBartFast


Too True!

I contend that most of our 'guns are plenty accurate considering the projectiles that we are dispensing. Someone stated in a post earlier that "a sphere is a shpere is a sphere" and that is true but I haven't seen many paintballs that are actually a true sphere. Most every paintball that I have seen and/or measured is a bit larger around or across the seem than it is when measured around or across the poles of the ball. It is also true that paintballs are filled with a material that is generally accepted as a "non compressable liquid" . Howerever, that liquid is contained in a relatively flexible container which is susceptable to distortion from the influance of the g-forces applied during the process of acceleration. Thus, when when acceleration begins, the flexibility of the shell allows the ball to tighten against the bore of the barrel and become somewhat cylindrical in shape. You can prove this out to yourselves with a very simple demonstration. Place a clean, unmarked ball in a barrel that you can blow it through with your own breath fairly easily. (a common "test" for proper bore sizing) Now blow the ball through the barrel and catch it in a soft cloth so you can inspect it closely (under magnification). After moving the ball through the barrel you will be able to see a small skid mark left on the surface of the ball; usually at two points near the seem of the ball. Now take that same ball and shoot it at game velocity through the same barrel at a bed sheet or similar hanging soft cloth that will catch the ball instead of breaking it on impact and again observe the size of the skid-mark left on the ball as it went down the barrel under pressure. You will see that the abount of shell that comes in contact with the sides of the barrel is significantly larger than when moved through the barrel with higher acceleration and g-forces. Now, the simple fact remains that the ball could not show a wider track on it unless it distorted enough to tighten the ball against the walls of the tube it is being pushed through. As the ball tightens and seals against the bore it has no choice but to become shorter in length, aka distorted by the forces of acceleration. Though not supported by a set of scientific calculations, the above demonstration and maybe a little basic comon sense, should prove to at least some of you that a paintball has to go through a lot of changes during the process of getting launched effectively. The trick to "effective" launching of a paintball is to understand that what goes on inside the barrel can and does effect what goes on shortly after the ball leaves the barrel. Internal ballistics do in fact influence external ballistics.
The most noticeable effect of improper propulsion characteristics (or tuning) is the amount of muzzle blast that can and does impart influence to the flight of a paintball AFTER it leaves the barrel. In short, the FACT of the matter is: if a mass of air blows past the not so round and somewhat flexible sphere after it has left the confines of the barrel, it can and does affect the flight of the projectile. Therefore, proper tuning and/or other means to control and minimize the muzzle blast are paramount to maximum effective range and accuracy. Proper tuning seeks maximum efficiency which in turn minimizes the effects of muzzle blast. You can also cut down on the muzzle blast effect with the application of a muzzle break to relieve and disperse excess air before the ball leaves the confines of the barrel. A short barrel with a long muzzle break (as is the case with many or most barrels these days) can and does help to compensate for an inefficient shot. That's why I started putting muzzle breaks and vented barrels on guns back in 1987.
In reference to Tom's high speed photography of many years ago, I seem to recall that was to address the condition of the ball at the point of or after leaving the barrel.
Tom, please correct me if I am wrong here. Also, is it possible that we can see some of those pics for ourselves?

If we really want to look at accuracy statistically, I already proposed a method for testing barrel length differences in another thread.

http://www.automags.org/forums/showthread.php?s=&postid=513906#post513906

[/B]

Statistics are only a guide, reality is definative.
That sort of testing was done many years ago only I did it with .5" increments of barrel length and did it with and without adjusting the valve output to accomodate the varying barrel lengths. My testing was also done at a fixed distance of 100 feet to minimize variables. The point of my tests was to establish what barrel length was needed to achieve the proper balance of efficiency and accuracy. Since the standard power source of the day was 12 gram cartridges, efficiency of the shot was very important and the first thing I noted was that as efficiency was improved, the size of the shot pattern on the target got smaller and the second notable point was that as velocity is increased, the shot pattern got larger. I also noted that a barrel that is too long suffers many of the same shortcomings in efficiency and consistency as one that is too short. Mainly due to the varibles of the painball's shape, size and weight.

In your test procedure you start with an 18" barrel and chrono the gun to 300 fps. My question is; when you cut the barrel down by 2" do you also adjust the pressure in the dump chamber to retain 300 fps or do you log the results of only cutting the barrel ? If you adjust the pressure to maintain a given velocity, you are effectively "tuning" the gun to suit the barrel; right ? If you start with an 18" barrel at 300 fps and start cutting the barrel down without making changes to the pressure or volume of gas being used to launch the ball, you should find that velocity will climb and the shot pattern will rise and get larger on the target for the first few cuts. Will you be able to understand the results ? Will you know why cutting a barrel down can often result in an increase in velocity? Are you sure that 300 fps is the best for testing since acceptable velocity limits seem to be coming down to 280-285 going on and 300 coming off? Also, for such testing purposes, you will find that the size of the shot pattern and whether the velocity goes up or down with each subseqant change will be the leading criteria for evaluation. Better effective range will only be indicated when the shot group rises on the target without changing anything other than the barrel.

But to say neither open nor closed-bolt makes a difference we're still debating those that would have us beleive there is some magical/unexplainable force working on the ball after it leaves the barrel. But they contend that it can be optimised for. [/B]

Since it seems obvious that I cannot "prove" to you that there is a benifit to closed bolt firing of a paintball (that is as opposed to traditional open-bolt firing as found in most blow-back operated guns) maybe you should present some substantiated facts that "prove" me wrong. However, you will have to change my mind and not just throw out a bunch of adversarial inuendo that would require the writing of several books to address effectively. Please keep in mind that I have a bit over 40 years of experience in dealing with guns and ballistics (internal and external ballistics) in general and nearly 20 years and tens of thousands of hours invested in finding and understanding the best way to get a paintball to go where and when I need it. On the other hand, I don't have a scientific or debating backround so I have to deal with what I know and what I see. No magic, no little elves no guessing; just a plain and simple reliance on reality.

[pbjosh]

Hitech-

half this thread is not about open or closed bolt, it is about people saying the guns will shoot the same distance. Spin is NOT included.

Actually I think, maybe not in this forum, but others, that it is something forgotten more than not.

And crucial to the Open vs. Closed debate.

We have gotten the knowledge that the gun will shoot the same distance shooting a ball the same speed, but, for the most part, people are still saying "Angels will shoot just as far as a Shocker because the ball leaves the barrel at the same speed." In fact a good chunk of the better brains this sport has.

And that just isn't correct. Some guns do shoot a bit further. Paint just flies into the ground when you shoot other guns. This is the way it is.

Why? Spin. Which is inherent in some guns. And the true center of this debate, NOT velocity.

Josh

[pbjosh]

Glen,

That is a very disturbing picture.

Josh

[Paladin]

Disturbing picture deleted.

Sorry. I did not think it would be offensive to anyone.

it has been deleted from my post.

[SlartyBartFast]

Originally posted by pbjosh
Personally-
Alot of people have taken the easy way out and said "all the guns firing at the same velocity shoot the same distance" but don't think that is right. Look at the Flatline barrels. That alone breaks the statement all to bits.
...

Saying the range is totally a factor of velocity puts you in the "Earth is Flat" group.

Josh

I think you'll find that the complete statement is:

"All markers shooting the same velocity shoot the same distance, except for the flatline barrels or Z-body Automag."

That's what the position has been in the umpteen other debates on this topic.

On a side note, my colleague who is heavily into firearms and shooting says that the only advantage between open and closed bolt action in a real firearm is for first shot precision/accuracy. But bolt them down to counteract the inertia of the bolt (which on an UZI approaches a couple of pounds) on an open bolt and there's no difference.

[pbjosh]

Glen,

I found the pic a bit disturbing, but it was really funny! It didn't offend at all.

Post it back up, I don't care-

Slarty,

You are missing something basic.

ALL gun induce spin. Some merely direct it.

Since all guns induce spin, some induce it more than others.

Guns that induce more spin are less accurate.

If a gun induced more forward spin it would be less accurate and have less range.

Hence, guns that induce the least spin are more accurate, and will have better range.

If a ball rolls into a barrel, incurring alot of forward spin, when it is fired it this will cause more forward spin, equalling less range.

Like I said, spin is in EVERY ball shot. Less spin means a more accurate gun.

Since EVERY gun induces spin, the factors of range are induced IN the gun, and are not SIMPLY a factor of velocity.

Josh

[_Spork_1]

Originally posted by billmi


Yes, I own WARPIG.com.



By "glossed" and "buffed" I assume you mean honed and polished. You are incorrect in this statement, the barrel was honed and polished.



That is also incorrect, the barrel is 11" long.

I'm not sure where you got the above data about the barrel used in that test. I can't find it in the article about that test, can you please point it out to me?



Which components of the barrel were variable? As far as I was able to observe, it's interior finish, length, and inner diameter remained constant through the duration of the test.

I will repeat my question from earlier, what are the criteria you place for a "good" barrel? Please, not something vague, specific criteria.



I agree a reg would have helped consistency. You would also note, that at the time of that test regs were not commonly used in paintguns.

While the consistancy may not have been easily predicted, it was recorded, and comparable in both the control, and experimental firings. That's why the chronograph was used, and why the order of firings were swapped up to take into account changes in the pressure and temperature of the CO2 tank.

See you on the field,
-Bill Mills

alright i used my friends sting ray before it was inaccurate in my mind, saw the balls going all over the palce, and the paint to barrel match was right

didnt know abonut the swaping to get the same fps for both clsoed and open

my thoughts, this is never going to be prooven either wayt, even though i slightly defended closed bolt with argueing the warpig.com test i do not think that it[closed bolt] is more accurate or less accurate or the same, i have no real results that will make my mind change at this moment, even though im neutural i still wont accept the stingray test as proof, too many varaibles to put in, (bad barrel(try a cp or something along those lines) ( bad gun, yes tons of people think "all guns shoot the same accuracy" but i think that some guns are better than others , hense the price marks

too tired after wrestling practise, proboly some typos and errors in m yrepsonse

[billmi]

Originally posted by _Spork_1

(bad barrel(try a cp or something along those lines) ( bad gun, yes tons of people think "all guns shoot the same accuracy" but i think that some guns are better than others , hense the price marks

I'll ask again.

Please define a "good" barrel, and what makes a barrel "crap." Since I don't believe that Dan at CP has magic dust to sprinkle on his barrels that make them good simply because they are CP barrels, how can we decide if a barrel is "good" or "crap" for a test? What are the criteria?

Same question for the paintgun.

See you on the field,
-Bill Mills

[billmi]

Originally posted by Paladin

Now, the simple fact remains that the ball could not show a wider track on it unless it distorted enough to tighten the ball against the walls of the tube it is being pushed through. As the ball tightens and seals against the bore it has no choice but to become shorter in length, aka distorted by the forces of acceleration.

I believe such wider "tracks" on the ball could also be achieved by the ball pitching and yawing during its travel down the barrel. Many have taken it as a given that the ball will face some rotation when fired - if the ball does in fact distort to this semi-cylindrical shape, such rotation would not be possible. Thus "hook" shots caused by a yawing spin couldn't happen.

I've had a look at some of the high speed video and stills Tom has taken of balls fired through a clear barrel (some is included in the Automag RT video.) If the balls are distorting, it is too insignificant to see in the photographs. An important question to which I hope Tom can supply an answer is, where those done with gelatin paintballs, or with Perfect Circle paintballs, which have a more rigid plastic shell?

Please also note, I will happily disagree with Glenn on theory or interpretation of the results of a test or experiment, but this in no way means I don't respect his viewpoint. There are a lot of people in the industry that will support a certain theory regardless of its validity, simply as a means to market their product. Basically they have a product, and whip up a theory to explain to you why it's the best in the world and you need to buy it. Glenn on the other hand, has used his theories of paintgun operation to build quality products, and is one of the few manufacturers/customizers to understand the concepts of old world craftsmanship.

See you on the field,
-Bill Mills

[AGD]

The balls in the video were run of the mill gelatin.

You guys keep thinking that spin has something to do with accuracy, I would like you to prove that with something other than conjecture. Linking baseballs to paintballs doesn't cut it.

AGD

[billmi]

Originally posted by AGD
The balls in the video were run of the mill gelatin.

That's what I thought, good to hear it confirmed.

You guys keep thinking that spin has something to do with accuracy, I would like you to prove that with something other than conjecture. Linking baseballs to paintballs doesn't cut it.

AGD

I would think the most straightforward way to document its effect would be with two-tone paint, and high speed photography as you have done.

From anecdotal evidence....

The Tippmann Flatline generates spin that has a noticable effect on the trajectory of the paintball. If the Flatline is turned 90 degrees on the roll axis and fired, the ball will lob like a normal paintball trajectory, but will hook to the left or right (depending on the direction in which the 'gun was rotated).

This hooking left or right is a behavior also sometimes seen (though not as severe) when firing paintballs out of a paintgun without any spin/no-spin design features.

Comparing this and photography AGD has taken of balls that don't spin in flight and seem to "wander" randomly in the vertical and right-left axes as they travel to target, it is reasonable to believe that a yawing spin can cause a ball to drift to the left or right of the intended target, and a pitching spin will create a vertical drift vector.

Certainly, more detailed experimentation would prove or disprove this hypothesis.

As for linking baseballs to paintballs, that brings up one of my pet peeves....

The next time someone talks about how paintballs can't maintain a spin because they are full of liquid, and "proves" it by the fact that a raw egg won't spin on a table but a hardboiled one will, throw an egg at them, because they want to play egg-ball. Then spin a paintball on the table and see how it does, and explain to them that paint fill is thicker, and doesn't have an inner sac connected to the shell with elastic like tendons.

See you on the field,
-Bill Mills

[Paladin]

Originally posted by AGD
The balls in the video were run of the mill gelatin.

Tom, I was going to ask the same question that Bill did but it seems to me that you did the high speed photography thing before you got started on the PC balls project. Is my memory serving me correctly ?
Also, what is your take on the idea that a paintball squats a bit against the force of acceleration and tightens against the bore when it is fired ? Don't we need the ball to tighten and seal against the bore if we are to expect any kind of consistency?

[i]

You guys keep thinking that spin has something to do with accuracy, I would like you to prove that with something other than conjecture. Linking baseballs to paintballs doesn't cut it.
AGD [/B]

Again, I don't know how to "prove" it but it has been my experience that the more spin seen on a ball in flight, the larger the shot group will be on target. Here, we strive to get our guns to shoot a "nuckle ball" with no spin at all. The actual flight of the ball looks a little erratic at times but they are more likely to be in a tighter group on target.
In the old days of single colored balls, it was hard to see what was going on but when we got paint with contrasting colors in/on the shell, it was much easier to see the results of our tuning process with just a few shots. If we see much spin on the ball in flight, the gun goes back to the bench to find out why and correct the problem. Oddly enough, we have found that we could minimize the amount of spin being imparted on the ball by insuring that the air flow through the valve, air passages and bolt was "clean" fast and non turbulant. Sort of like the concept of "porting and polishing" the heads on a high performance engine. Quite often, we can drastically improve on shot-to-shot consistency, efficiency and and accuracy with just a minor correction to the shape or condition of an air passage between the valve and the face of the bolt. I've seen numerous instances where 5 seconds with a Dremel tool to champher one corner of an air passage can improve velocity by 20-40 fps; which in turn means that the shot will be more efficient, the ball will get up to speed quicker, more consistent and generally more accurate.

[billmi]

Originally posted by Paladin

I've seen numerous instances where 5 seconds with a Dremel tool to champher one corner of an air passage can improve velocity by 20-40 fps; which in turn means that the shot will be more efficient, the ball will get up to speed quicker, more consistent and generally more accurate.

Glenn,

In a previous post you said the open/closed bolt accuracy test did not show a difference between bolt position because the test gun was not tuned for optimal closed bolt performance.

Would it not be a possibility that it's the tuning that is optimizing efficiency and consistency in the gun setup, rather than bolt position that has provided the improved performance in your experiences?

Se you on the field,
-Bill Mills

[pbjosh]

AGD-

Proving spin on the ball affects accuracy? That is a given. The balls spin when they leave the gun. All of them do.

Conjecture? Magnus affect, boundary layers and all that:

http://www.geocities.com/k_achutarao/MAGNUS/magnus.html

http://www.lerc.nasa.gov/WWW/K-12/airplane/bball.html

http://www.lerc.nasa.gov/WWW/K-12/airplane/beach.html

http://landau1.phys.virginia.edu/classes/311/notes/aero/node2.html

http://www.newscientist.com/lastword/article.jsp?id=lw387

And that is just the TIP of the iceberg. We are still dealing with a ball, which at 200mph makes for alot of interesting affects moving through an atmosphere. Spin is the entire issue for accuracy and range.

Bill-

As for the egg reference, tell them to throw an egg. Does it stop spinning? I can't throw an egg far enough for it to stop spinning before it hits, but that might be me. It does slow down...........hmm...........time for testing?

Glen-

What you were doing with tuning the valve is what I was trying to do with the 'Shiva' project. I found my valve is still a bit to harsh at 160psi, but the effeciecy and accuracy are both very good. A clean tuned port makes for an accurate gun in my opinion.

Josh