Barrel Efficiency, Tech Tip #1

[AGD]

Guys,

I have decided to do a tech tips series of posts so you will understand certain technical processes that go on in the paintball gun. We have tested everything I will talk about and any speculations will be pointed out.

In the tech forum there is a long post on what is the most efficient barrel so here are the facts.

Barrel Efficiency, Tech Tip #1

Barrels are only there to accelerate the ball from a standstill to 300 fps. In theory they also help with accuracy but that's another post. The ball goes through incredible acceleration on its way down the barrel. The balls acceleration rate is approx. 50,000 feet per second to get to 300 feet per second in 10 inches. The entire barrel travel time is about 6 thousandths of a second and this means the ball is seeing about 1500 G's when its getting pushed out the gun. Although this may sound incredible if someone out there would like to do the math you will see that I'm close.

Air pressure behind the ball is what causes this acceleration to happen. This pressure varies between the different guns but is generally between 50 to 125 pounds per square inch at its peak. The air pressure peaks right when the ball starts moving down the barrel, after that, the ball moving down the barrel creates a bigger chamber so the pressure drops. This is why low pressure guns are a myth, in reality all guns shoot at considerably lower pressure than 200 psi.

Peak pressures above 150 psi tends to break balls down the barrel due to really high acceleration and G forces. If you don't have any way to control the peak pressure behind the ball, the only way you can change it is to go with lower pressure in the air chamber, hence low pressure guns. AGD uses the precise contour of the power tube tip to release air in a controlled manner behind the ball to limit peak pressures to around 60-80 psi..

It is simple to understand that the harder you push something the faster it will accelerate and get up to speed in a shorter distance. So what distance do we have to get the ball up to speed? The effective length of the barrel is from the balls position before it's fired, to the place in the barrel where the pressure gets released, This is usually at the first porting holes or the step in the barrel. Porting is there to release gas pressure!! You are effectively stopping the acceleration at the ports so your 14" barrel that is half full of holes only has an effective length of 7".

Now we understand that we need to limit the peak pressure behind the ball to keep it from blowing up, and that the pressure drops as the ball moves down the barrel. The next question we need to ask is, how far down the barrel does the ball have to go before the pressure gets to low to do anything useful? That answer is 8-10 inches. We know this from looking at the graphs that our gun dyno puts out. If your peak pressure is higher, say over 100 psi you can get away with a shorter barrel, if it's lower then you need a longer barrel. Since AGD is the only gun manufacturer to actually test their pressures behind the ball you might have a hard time getting this info for other guns.

So as far as our guns are concerned, the best efficiency would be had with an 8-10" effective length barrel. Since two piece ported barrels with an effective length of about 5-6" are the rage right now you hear a lot of complaints about gas efficiency. Under some circumstances there is a good reason to use a short effective length barrel. Short barrels cut off the acceleration abruptly by venting and this has the effect of tightening up the shot to shot velocity variation. If you need this at the expense of efficiency then go ahead. Tighter velocity control usually translates into some improvement in accuracy due to better consistency.

So if you want the best of all worlds, limit your peak pressure, let your ball accelerate all it wants, don't follow the crowd and keep asking questions.

AGD

[Miscue]

Hey now! This is a great idea... hope you have a permanent place to put this so we can all go "See, I told ya so, says right here." http://www.automags.org/ubb/smile.gif

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'Sacrifice the Body'
68 PF - HyperFrame - 68 Flatline - SS BigShot

Miscue's Profile (http://www.liquidmagma.com/automags/miscue.php)

[Allen]

Gee, I've been telling people that before... Not with the exact numbers, though. Plus I am no rocket scientist. 12in Lapco Bigshot-"effective" length of around 10 inches. I don't have mine here to measure, but the only porting on the thing is in a band right before the muzzle break.

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"Don't spend so much on parts that you can't afford to play."

[X-Plosive]

For those of you who don't understand a Barrel that has more effective barrel length is more gas effecient. Effective barrel length is the portion of the barrel that is unported. However barrels with less effective barrel length and more porting give you tighter shot grouping(more accuaracy). I know Tom explained it well but I didn't understand at first I thought I might as well simplify it further.

[manike]

<font face="Verdana, Helvetica, sans-serif" size="2">Originally posted by AGD:
Barrels are only there to accelerate the ball from a standstill to 300 fps. In theory they also help with accuracy but that's another post.</font>

I'd like to read that other post please when you get time http://www.automags.org/ubb/smile.gif

thanks

manike

[Dubstar112]

Finally Im going to make use of my printer

[Dubstar112]

oh yeah and that means the 98 only has like 4 inches of barrel.... damn

[luke]

Cool, meat and potatoes, I like it!

[cphilip]

Sorry to hear you are in "rain delay" but you loss is our gain. You got time on your hands huh? http://www.automags.org/ubb/wink.gif

Phil

[DarkRipper]

Good information. Stuff I've known about (except for the AGD testing info) but still a good refresher.

http://www.automags.org/ubb/smile.gif
DR

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Owned a PF mag in 96.
=)

[azzkikr]

isn't it nice to know and talk to someone who knows what they are talking about. Later AZZKIKR

[Jeb_Hoge]

What about bore sizing? Is it as substantial an issue as it's been made to be lately, or is it not so important (ref. the Palmer theory of the paintball distorting under the initial impact of the airburst so that all sides are in contact with the barrel breech when acceleration begins)?

[luke]

Jeb_Hoge,

EXCELLENT question! AGD..............

[FeelTheRT]

how does a stock Emag/RT barrel's efficancy compare to a 12" DYE one peice barrel..?

[LCDmag1]

So the effective barrel lenth is before the porting starts on an unsteped barrel.

[Speed_Mag_22]

whoa... i actually learned something... Gun Dyno's! http://www.automags.org/ubb/biggrin.gif

[chaoticorigin]

The Dye 12" one piece has 7" of unported length. Shouldn't I measure the length from the beginning of the paintball? It would be less then. I was thinking of putting tape around the gun end of the porting covering about an inch so wouldn't that in effect make the barrel more efficient?

The 2 piece dynamics confuses me a little. As the paintball goes to the 2nd step. Doesn't the ball continue to accelerate until it hits the porting? I think the acceleration should still continue but at a lower acceleration because the bore is larger. I gotta try some experiments this weekend with a boomstick. I heard 8-12 was the ideal unported barrel length.

Why doesn't AGD make some good barrels as an optional buy? They seem the most serious about paintball dynamics. My stock barrel shoots decent but it doesn't have a mirror finish interior which gives less friction.

[kero]

Excellent info. Now this is quality service to your customers http://www.automags.org/ubb/smile.gif

Keep it coming and many thanks. Maybe sometime you will address the biggest paintball myth... that closed bolt guns shoot farther than open bolt guns.

[JRSJKD]

This is exactly why I've played with a mag for over ten years. AGD never talks any smack about other manufacturers but if you ask the right question they will give you the answer and back it up with real science and data. From there they let us make a decision based on fact not hype.

Tom, is www.paintballphysics.com (http://www.paintballphysics.com) ever going to become a reality or will the info just be put in the tech tips area?

[Allen]

Speaking of closed bolt vs. open bolt-

http://www.warpig.com/paintball/technical/paintguns/balistic/closedopen.shtml

Who other than WARPIG and AGD should we rely on to confuse us, stun us, educate us, and entertain us?

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"Don't spend so much on parts that you can't afford to play."

[splatterp8nt]

Thumbs up to AGD for their markers, their advice and the awesome customer servie they provide.

[manike]

Now paintballphysics.com is definitely a site I would like to see.

Open up those archives and show the world some real data http://www.automags.org/ubb/smile.gif although the 2inch folder on mag bumpers could probably be left in the draw... http://www.automags.org/ubb/wink.gif

I would really like to have that film of the ball being shot through a glass barrel available for all. The close up of the ball in the breech and the ball exiting through the smoke trail (I know there's a bit on the RT video). As well as the ball in flight, that stuff is amazing to watch.

I also think some barrel testing with and without ports and some sort of trace element in the gas to actually see if it does exit the ports behind the ball as it goes past would be very interesting!

How about a new breed of two piece glass barrels lol... gotta keep up with fashion http://www.automags.org/ubb/smile.gif

manike

[FireWall]

So whats the Dilly? Why do they put porting on barrels then??

[FlipFlops]

manike, along with glass barrels we'd need colored N2 :-)

[-§on-]

WoW, Tom To Much Spare Time... http://www.automags.org/ubb/biggrin.gif

[Webmaster]

HEY MANIKE! Nice to see you on here, mate! Sure theres lots of stuff you can contribute!

take care!

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Webmaster - AutoMags.Org
webmaster@automags.org
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"Good...bad...I'm the guy with the gun." - Ash, Army of Darkness

[Hoyahdestroyah]

Great info!! That's why AGD makes the best guns in the business.

[PCI2000]

Firewall,
Porting is there to release gas pressure and to quiet the sound. An unported barrel is very loud when you fire a paintball through it.
So it's like a tradeoff:
Unported = loud but more gas efficient
Ported = quieter but less gas efficient

Gotta find that happy medium ssomewhere...

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Black Teflon ReTro Mag (http://albums.photopoint.com/j/View?u=1575476&a=11977518&p=43135827&Sequence=0&res=high)
Warped Sportz Drop Forward
68ci/4500psi Centerflag Hyperflow 420 tank
Benchmark 45 grip frame w/Dye sticky grips
KAPP foregrip extender w/Benchmark foregrip

[manike]

<font face="Verdana, Helvetica, sans-serif" size="2">Originally posted by Webmaster:
HEY MANIKE! Nice to see you on here, mate! Sure theres lots of stuff you can contribute!

take care!</font>

OK I'm wondering who the webmaster is... My Yanky friend John? How's the theory of light speed travel going? And the Religious debating?

or another of the crew http://www.automags.org/ubb/smile.gif Eric?

It's not one of the brit John's is it? Hiding behind a Kansas City Origin, lol.

I have a suspicion it's Bonich, but the US origin bit is throwing me... If it is JonBon we need to talk some CAD/CAM stuff matey http://www.automags.org/ubb/smile.gif

Ahh just had a thought... it's not Mr44 is it?

Bill posts under something else so it aint him, Dawn? .... aarrrgghh too many possibilities http://www.automags.org/ubb/smile.gif

manike

[This message has been edited by manike (edited 06-19-2001).]

[M-a-s-sDriver]

Man, I hate to do this: I believe you have the acceleration rates wrong. They are a bit overstated. The rate to push the ball is not 50,000 fps. That is about the escape velocity to achieve earth orbit. To hit that number in 10 inches would push the g-forces to over 22,000, enough to permanetly compress titanium. If you are talking about the initial acceleration from zero to any number, that is proportionally the highest attainable acceleration number on the curve, and mathmatically approaches infinity. Also, if you did go to 50,000 fps, you have to decelerate the ball down to the 300 fps mark and therefore put the paintball through double the stress. Am I off-base here, or did I miss something? Brent Jackson, Pink Fluffy Ballerinas.

[SniperWolf]

glass barrels eh? take a look at the new pirhana barrel, clear. theyre made out of polycarbonates i believe, like bullet proof glass. now about this effective length, i understand that porting makes it less gas efficient, but does the porting really vent all the accelerating gas that early? wouldnt the severity of the porting also dictate effective length. like the 98 barrel, it has a ring of porting very early on, but is that venting area enough to blow off all that gas i dont think so. and the palmer theory, palmer is a very smart guy, but their is video where someone powdered the barrels and shot through it, and showed that a paintball rides on the 2 highest points, like rails. so palmers spoken like a man who doesnt makes different bore barrels. though he does have elliptical honing, which is a whole other barrel of monkeys http://www.automags.org/ubb/tongue.gif

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Frag'd, toe tagg'd and body bag'd,
hell son, you mustve just been automag'd

[hitmanng]

Jerk is a mechanical term for a specific aspect of motion: the rate of change of acceleration with time or in this case ft/sec/sec/sec. I do not believe that is what Tom is using.

Velocity is defined as the rate of change of position with time, and measured in paintball as feet per second.

Acceleration is the rate of change of velocity with time; acceleration is measured in paintball terms in feet per second per second.

Jerk describes the way acceleration itself changes; it is reckoned in the even more unwieldy units of in paintball terms feet per second per second per second.

A paintball accelerates from 0 ft/sec to 300 ft/sec over 0.83 ft if the rate of acceleration were 50,000 ft/sec/sec the time period would be 0.006 seconds
That's 300ft/sec / 50,000 ft/sec/sec = 0.006 sec
The acceleration of gravity is 32 ft/sec so That's 50,000 / 32 = 1562.5 G
I believe those are the numbers used by Tom above.
Tom is using acceleration here and simply forgot or figured most wouldn't understand or care about the units used. I know I didn't care as it was not needed to understand what he was trying to say.

Last week Phase chemistry, this week physics. Maybe next week we will look into molecular biology. Maybe Organic chemistry study up on your function groups.
Tom Kayes paleantologist, astronomer, enginer and physicist.
Now right now Army is going. Wow all that and he cannot even spell. LOL
Hitmanng


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"I would rather hit once than miss 140 times."

[DarkPhoenix]

Porting also helps the paintball in its movement through the barrel. The porting helps bleed off the air in front of the pball as it moves forward, because the paintball also has to deal with the pressure of the air in front of it, in an non-ported barrel, I believe the air in front gets a little compressed and the paintball must overcome this pressure, so porting and the barrel break help in this regard. I may be complete off base here, but I believe that these are other factors that come into play when considering barrels, as non-ported barrels are usually louder but more gas efficient, while ported barrels tend to be quieter, less gas efficient and, some say, more accurate. It is my personal belief that this accuracy is obtained by the effective venting of the pressure both in front and behind the ball. Though, I have been known to be wrong before....

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RT Pro P/F
w/ AGD Flatline

[RobAGD]

Actually Tom has high speed vidoe of that.

There is nothing being pushed out the end of the barrel by the ball. It was long held that the ball would be pushing a colum of air out BEFORE it exited the barrel.

Toms high speed video shows that the onlt thing exiting the barrel is the Ball then a gas plume. The Smoke was intact until the ball broke its plane.

-Robert

[MajorDamage]

PORTING! Porting also helps with ACCURACY! Imagine shooting a bullet into the water, it just curves like crazy and stopps. Its thesame with paintballs pretty much. But the holes in the barrel slowly get the paintball used to the air, helping it to not just be suddenly introdued into the air. SO THATS WHY PORTING IS GOOOODA!

ENDO!

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My Battle cry!
Spoon Spork Purple Monkey Dishwasher Hoo Ha!

[SHAG]

Hi,

The fellow above does have a point and I would like Rob or Tom to elaborate this in more detail. I remember in the AGD video that Tom discussed the "new" Crown Point barrel. He was mentioned it ressembled the V ducts on Indy cars. Also it was to aid the ball with a smoother transition into the air. What happened with the CP barrel design? Other than that, Tom, Glenn, and Colin have alot of time in barrel design. I feel they are on track when it comes to the barrel. The best barrel design that does mix the effective barrel length and porting is the J&J Ceramic. It is the best of both worlds.

Later,
Alan

PS Nice to see on here Jeb

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Paintball cannot be that big. No one has really been able to sponsor a stock car or a race yet. (local people do not count in this case :))

[klm5]

Thanx for the info, I'll do some side-by-side comparison shooting with my AA & shorter, un-ported Armson.

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68PF,Boo-Yaah frame,SP AA 14",Shocktech cradle

[hitmanng]

You have to remember the speed of travel, and excelleration here. The ball is moving faster than the air could "Move out of the way". Playing in a vaccum would be great but not an option. The Idea of the crown point was to create a gradual transition from the air in the barrel to the air outside the barrel. I think it never took off because with all of the forces on the ball the crown point was not he most important factor. Do you realize that we can hit a can with a gellatin paintball, filled with fluid, 50 ft away, being propelled by air. That is a remarkable feat. I think asking for much more is too much. The fact is you can do this with most barrels. No new designs can overcome all of the uncontrolable factors.
Hitmanng


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"I would rather hit once than miss 140 times."

[Webmaster]

Manike -

Sorry for the later reply

Yes - it is Mister.44

cheers!


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Webmaster - AutoMags.Org
webmaster@automags.org
----------------------
"Good...bad...I'm the guy with the gun." - Ash, Army of Darkness

[The Taoist]

Great post tom. Very helpfull information. webmaster (aka Mister.44), just wanted to let you know that i enjoy you reviews / articals in APG. Good work guys!!

[randomboy]

Its amazing what you can learn just sitting here at the computer http://www.automags.org/ubb/wink.gif

[manike]

Cool good to see you http://www.automags.org/ubb/smile.gif

I guess things worked out then!

Gonna be at the Cup this year? I'll be over for it again http://www.automags.org/ubb/wink.gif

manike

[randomboy]

Oh yeah, and damnit, I completely missed hitmanng's thread yesterday, then thought of that answer while at work today http://www.automags.org/ubb/wink.gif 50,000/.006 = 300

I slapped myself in the head for not realizing it sooner. haha. And to think I just got out of physics class a month ago, what a shame.

[PyromaniaX]

so what about ram rods? That would make them have like 1 inch of effective barrel.

[M-a-s-sDriver]

Well, I've been thinking about this, and the conclusion I come to is that there painty-ball thingy Does not, cannot, would not, and is completely unwilling to go 50,000 feet per second, no matter how much to beg. The problem with the formula (50,000 x.006 =300) is that you are assuming the paintball travels 300 feet in .006 seconds, because that is how fast it would have to go in that amount of time to hit 50,000 fps. A mile is 5280 feet. For this logic to work, it means that poor little paintball has to go 2840 miles per hour. That is approximatly mach 4. That is the muzzle velocity of a .308 sniper rifle. (ARMY, step in here if my ballistics are wrong buddy). A paintball has a muzzle velocity closer to an arrow released out of a 70# bow.
Now, If that ball got anywhere NEAR 50,000 fps, you would have to decelerate the poor thing back down to 300 fps somewhere in the barrell. Unfortunatly, all the two piece extremme porting in the world won't do that.
Sorry guys. The math is wrong here. Think about it some more and you will see.
Respectfully, Brent Jackson, PFB.

[keebler]

well actualy chuck at co paintball in toledo ohio showed me a pic of this 3 foot (i think it was that long) barel he messes around with his angel. lol, that thing might do the job.

[hitmanng]

<font face="Verdana, Helvetica, sans-serif" size="2">Originally posted by M-a-s-sDriver:
Well, I've been thinking about this, and the conclusion I come to is that there painty-ball thingy Does not, cannot, would not, and is completely unwilling to go 50,000 feet per second, no matter how much to beg. The problem with the formula (50,000 x.006 =300) is that you are assuming the paintball travels 300 feet in .006 seconds, because that is how fast it would have to go in that amount of time to hit 50,000 fps. A mile is 5280 feet. For this logic to work, it means that poor little paintball has to go 2840 miles per hour. That is approximatly mach 4. That is the muzzle velocity of a .308 sniper rifle. (ARMY, step in here if my ballistics are wrong buddy). A paintball has a muzzle velocity closer to an arrow released out of a 70# bow.
Now, If that ball got anywhere NEAR 50,000 fps, you would have to decelerate the poor thing back down to 300 fps somewhere in the barrell. Unfortunatly, all the two piece extremme porting in the world won't do that.
Sorry guys. The math is wrong here. Think about it some more and you will see.
Respectfully, Brent Jackson, PFB.</font>

Sorry M-a-s-sDriver,
But you have your units wrong here. The ball does not travel 50,000 ft/sec the speed of sound is 1,088 ft/sec and the paintball does not even approach the speed of sound.

It does however excellerate at a rate of 50,000 ft/sec/sec. Acceleration is the rate at which velosity changes. This means for every second that passes the balls velosity would change by 50,000 ft per sec. So in 0.006 seconds (the amount of time it is in the barrel) it changes from 0 to 300 fps. The math stands as
50,0000 ft/sec/sec X 0.006sec = 300 ft/sec
Please note the units used.
Please do not take this the wrong way. I am only trying to explain and if it sounds condicending I am sorry. Physics is one of my favorite things.
Hitmanng


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"I would rather hit once than miss 140 times."

[M-a-s-sDriver]

I'll buy that, math-wise. But that would require that the ball go 300 feet in .006 seconds. Rather, in that amount of time it really only goes about 10 or 12 inches, at which point it has reached it's terminal velocity. Now if you carry out the math, and assume it goes 12 inches, or 1 foot in .006 seconds, 300x.006 is 1.8 seconds. Now that still does not equal 300 fps, obviously, but we are getting close. So far I am off the actual fps number by 80%. The other method is off by about 10,000 %. Even if you use the arguement of RATE of acceleration, that would mean that that paintball would have to reach terminal velocity in roughly 1/180,000 inch, then maintain that velocity through the barrel. The simplest way to visualize this , again, is with a bow and arrow, since the terminal velocity of an arrow and a paintball are almost identical. A typical arrow is approximatly 28 inches long, which makes it about twice as long as a freak barrel, which I have. That means, according to the 50,ooo fps principle, that somewhere along it's path on the bow, it hits a rate of 25,000 fps, which is impossible. Part of the problem here is the expression of 'rate'.
Naturelly, if you CONTINUE to accelerate an object, at any rate, it will achieve the desired terminal velocity. But we have only a small length to propel the ball, and it's terminal velocity is the highest speed it reaches.
Now remember guys: You are thinking I am a completely brilliant person to have these great thoughts, but I have consumed 4 Sierra-Neveda Pale ales, So my thinking is on an entirely different level from yours. (you have to determine which level though).
Again, with the utmost respect to those here, Brent Jackson, PFB.

[hitmanng]

<font face="Verdana, Helvetica, sans-serif" size="2">Originally posted by M-a-s-sDriver:
But that would require that the ball go 300 feet in .006 seconds. </font>
No actually it says 300ft/sec so it would take 1 sec to go 300 ft.
Say the barrel is 12 in or 1ft long. To traverse it in 0.006sec the average speed of the ball is
1 ft / 0.006 sec = 166.7 ft/sec.
(Actually the barrel must have been about 10.8 in long so the average was 150 ft/sec)


<font face="Verdana, Helvetica, sans-serif" size="2">Rather, in that amount of time it really only goes about 10 or 12 inches, at which point it has reached it's terminal velocity. Now if you carry out the math, and assume it goes 12 inches, or 1 foot in .006 seconds, 300x.006 is 1.8 seconds. </font>

Look at the units here. 300ft/sec x 0.006 sec = 1.8 ft. This is true if the ball were moving at 300 ft/sec the entire time it was in the barrel it would have traveled 1.8 ft but it was accellerating so only reached 300 ft/sec as it left the barrel.


<font face="Verdana, Helvetica, sans-serif" size="2">Now remember guys: You are thinking I am a completely brilliant person to have these great thoughts, but I have consumed 4 Sierra-Neveda Pale ales, So my thinking is on an entirely different level from yours. (you have to determine which level though).
Again, with the utmost respect to those here, Brent Jackson, PFB.</font>

I do agree you are on a different level at this point LOL.

Use the units in the equations it helps. The ball never goes 50,000 fps it could not. It never passes 300 fps. Acceleration, Velosity and distance are very different and the numbers do make sense.

The accelleration in the barrel is 50,000 ft/sec/sec.
The average speed is 150 fps with the lowest speed being 0fps and the highset speed being 300 fps.
The distance is 10.8 inches and the time is takes to travers it is 0.006 seconds.

Hope this helps,
Hitmanng

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"I would rather hit once than miss 140 times."


[This message has been edited by hitmanng (edited 07-21-2001).]

[Motomaz]

I never knew that I could learn so much from paintball on a website. This is so cool about the barrles. I found that the stock barrle isn't really that bad but it may break paint more then a aftermarket barrle will. I have a 12 inch boomer and it seems that I never break paint. If I do break paint it's on people http://www.automags.org/ubb/smile.gif

Andrew