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Old 09-12-2006, 06:53 PM   #21 (permalink)
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Avery... with my Apex Elite at spring castle I had no paint to barrel match (the balls would just roll out) but the burst of gas alone was enough to give the ball good flight... not perfect but predictable and at good velocity. Which goes along the lines of what Mike does with the Phantom and the sizer rings... so long as you haev a tight seal at the start.. who cares what happens down the rest of the tube.

Definately something to play with, but I'm sure there is no single correct answer.

E

Last edited by Schmitti; 09-13-2006 at 10:10 AM. Reason: Had to add Elite.. as some one has resurected an old name for a gimmick product..bastids
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Old 09-13-2006, 12:20 AM   #22 (permalink)
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Quote:
Originally Posted by Schmitti View Post
Definately something to play with, but I'm sure there is no single correct answer.

E
There is a single correct answer. The laws of physics and their application to ballistics.

The problem is; that in paintball ballistics there are endless varibles that cannot to controled. By far the most significant varible is the paintball itself. They are not perfect spheres, their size and shape are dependent on temp and humidity. Their wieght is fairly consistent I have weighed dozens and was surprised at how consistent the weights are. Then there's hardness; how much the ball distorts when it is impacted by the pressure behind it. Size and shape of the chamber, how far it travels before it enters the constriction of the barrel, how the seam is oriented in the bore.

There are many more; porting, barrel crown, step up in bore size etc. The list seems almost endless, of course pressure and gas volume and type.

The question of when a projectile quits accerlerating is dependent on the pressure curve of the propellant. That is, at what point does the charge stop expanding? Where does the pressure peak in relantion to how far the projectile has traveled down the bore. I know the 8 to 10 inch number is used often, maybe it's accurate but maybe not, depends on the varibles stated above. However at some point the energy behind the projectile is expended.

If the energy is expended (pressure has peaked) while the projectile is still in the barrel it instantly begins to declerate due to barrel friction and the pressure wave that is created in front of the projectile traveling down the bore. The porting also helps to relieve this pressure wave too.

If the propellant is still expanding when the projectile leaves the bore it instantly begins to decelerate as well. As soon as it leaves the bore the pressure drops, it is no longer contained, and no longer acts upon the projectile it is dipursed in all directions. At the moment of exit the projectile is traveling faster than the propellent. It is slowing due to air friction and the pressure wave created in front of the projectile. Air density, temp humidity etc.

Its like pushing a car, once you stop pushing, it starts to slow down.

I doubt that the pressure peaks in a ported PB gun barrel at the point the ball exits the muzzle due to the poor seal between ball and bore. Once it hits the first port pressure begins to drop. Probaly drops much sooner due to the sloppy ball to bore seal.

Of course I have no way of knowing, but in an unported barrel of 5 to 6 inches I would think that the propellent could be still expanding (pressure has not peaked) at muzzle exit.

Even under lab conditions I would think it would be very difficult to draw any hard conculsions about PB ballistics with off the shelf goods. We would most likely end up with a few more general rules of thumb.

I bet the first thing any researcher would do is set out to create the perfect paintball.
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Old 09-13-2006, 02:14 AM   #23 (permalink)
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Schmitti, how does an APEX work exactly? I have been trying to figure it out, but, I'm kinda lazy and other forums scare me.
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Old 09-13-2006, 09:01 AM   #24 (permalink)
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My personal favorite length is 10" ported.
Robertsr,
Do you have a PPS barrel on your Sniper/ cocker? How do you like it?
Actually no. I have a 12 inch ported Custom Products which I like quite well.

However it's nowhere near as accurate as my 10 inch unporteds on my Blazer and my Mag.
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Old 09-13-2006, 10:09 AM   #25 (permalink)
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Sorry Bill I meant an Apex Elite, which is a nelson based pump.. (not the barrel gimmick thingy)... they work well if you can get paint that fits.

Pardini.... laws of ballistics.. a sub study of of physics, say there are two ways to get a projectile to the target.. and that's based on angle of trajectory.

I agree with what you have stated.

As to weight of the ball, that's just part of the filling process, each ball gets a certain weight of fill (which will vary ever so slightly)..and the other variation is going to be in how much moisture is lost from the shell as it dries... which is going to be slight.

As you said it all depends (really) on what type of gas is used as a propellent.. and in the case of CO2 how it is used. CO2 has extreme potential energy when compared to HPA, due to the fact it is changing states from a liquid to a gas under pressure and then again to a gas under relatively low pressure.... those phase changes will release an extreme amount of energy. And that's if you are feeding the gun with liquid CO2... for a gas gun it's going through one phase change.. and high pressure gas to low pressure gas isn't truly a phase change.

Anyways.

You are generally correct in your statements... when it comes down to it a few things can probably be dropped due to negligible effects (such as barrel crowning).. and for any testing constants should be used... smooth constant bore (no porting, no bore change and no overbored breach).

As to a perfect paintball... one in a trillion chance of creating one..maybe? They've tried hard... I think now though the industry has us in a choke hold with us the buyers "allowing" them to sell multiple paint sizes.

E
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Old 09-13-2006, 10:47 PM   #26 (permalink)
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I think barrels are odd. I have shot dozens. When they are made well to good tolerences - they all seem to shoot the same to me.

A good quality barrel seems no different from any other good quality barrel.

The paint is the difference.

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Old 09-13-2006, 11:07 PM   #27 (permalink)
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I've given up on barrels long ago. I've shot stock cocker barrels with crappy paint that were dead-on. I've shot draxxus x-ball through my freak kit and they've hooked like mad. It's about what kind of mood a particular barrel is in on a particular day.
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Old 09-13-2006, 11:10 PM   #28 (permalink)
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I agree that bad paint is the key.

Also for a lab experiment. Perfect Circle, Tom Kaye's company, does make circular balls for us to shoot out of our paintball guns. If we want to eliminate poorly shaped spheres out of our equation than some plastic perfect circle ball is the way to go. No doubt they arent "perfect" but I bet they are pretty close, and good enough.

Unfortunately it also modifies the idea that the ball is smashed when it is blasted with air..we do know that it doesnt smash very much though because of tests done with a visual aid, some powder or whatever, that shows the balls 3 point track down the barrel. If the ball really did get compressed it would make itself fit the bore.

Also most inaccuracy caused by a short barrel could be from air turbulance when the ball is being blasted into the nice calm outside air. Because of this, a guns accuracy could be better than anothers..with the same paint and barrel. Could.

Things like firearms and pellet guns dont get this turbulance so much because they dont have the huge surface area compared to to their speed and mass, that a paintball does.

Im just talking.
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Old 09-13-2006, 11:34 PM   #29 (permalink)
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Let us not forget one very big variable in paintball that you do not get in firearms, the big liquid center that moves in a way and speed not always in line with the shell
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Old 09-14-2006, 09:39 AM   #30 (permalink)
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I think much of the physics that is applied to paintball is theory.

It reminds me of all the physicists that attempted to explain why Coke and Mento's created such a reaction. Some had parts of the explanation, some had nothing. All were viable theories until the testing began.

Paintball has had very little testing, except for a few tests by Tom Kay and the like, to know what really effects it. We have theorized that the fill moves at different speeds - we have never tested it. We theorized that the ball gets compressed when shot - we know it has little visual effect once it leaves the barrel - but I have never seen a test of how it acts in the breach. We have theorized that rifiling goes nothing, but then had much anecdotal evidence that internal rifling of Armson and J&J barrels really worked.

I tire of reading the arm chair Engineers and Physicists theorize over the impacts of a paintball with no real testing. They are simply philosophers at that point - and that is best left to those who are studied in the field of philosophy.

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