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How longer and tight bore effects shooting?

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Old August 30th, 2012, 02:20   #1
highny
 
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How longer and tight bore effects shooting?

Hey guys.

I'm looking to upgrade my new gun and I figure inner barrel should be a good place to start.

Could anyone tell me the effect of long vs short inner barrel?
Example, m4(363mm) vs m16(509mm)

Another decision would be tight bore. What effect does it play?
Difference between 6.03 or 6.01.

I understand the length and port ratio but if you know a place were I could gather more knowledge on inner barrel please let me know!

Thanks.
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Old August 30th, 2012, 02:59   #2
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Barrel length

The barrel length is mostly associated with accuracy, as a longer barrel will stabilize the projectile longer and therefore creates a straighter trajectory. While this is basically true, this effect is most probably a bit overrated in the realm of airsoft. Much more important is the length in relation to the volume of air that is compressed in the cylinder. If the air volume is too high for a certain barrel length, the BB will still be accelerated shortly after it left the barrel, which possibly destabilizes the flight path. If the air volume is too low, the BBs canít be fully accelerated, wasting potential velocity. Therefore various cylinder designs are available, bore-up ones with a bigger volume as well as those with holes at different areas, reducing the utilized volumes to match the respective barrel length.
Another difference the length can make is the muzzle velocity. The longer the barrel, the later the BB will leave the barrel and the longer it will be accelerated, provided the air volume is sufficient to use the length. Another tricky behavior here is again the difference that various BB weights can make to the muzzle energy. If a heavier and a lighter BB is used in the same barrel, the heavier one is travelling slower and therefore stays longer in the barrel, giving it more time to accelerate (again, provided the air volume is sufficient). This means that a heavier BB, although its muzzle velocity is still lower compared to the lighter one, will have relatively more muzzle velocity than it should have according to the velocity conversion explained in the beginning of the article. Thus it has effectively more muzzle energy than the lighter BB fired from the same gun. This is something that should be considered while checking fps limits for a game. This effect is even more common with gas guns, as the amount of propellant per shot in those guns is most often much higher that than needed in stock configuration, meaning that nearly every increase in barrel length and/or BB weight will result in more muzzle energy.


Barrel diameter

The barrel diameter has quite similar effects. A tighter bore results in less leaked air, meaning that more air is utilized to accelerate the BB, thus it creates a higher velocity. The effects on accuracy however are quite debated. One could assume that a tight barrel will stabilize the BB better than a loose one, however much more relevant is the regularity of the inner surface. Also a certain amount of air cushion is needed to prevent the BB from touching the barrel surface, which would destabilize the trajectory as well as the amount and angle of the backspin, created with the hopup. So too tight is as bad as too loose.


By http://www.airsoft2day.com - World Airsoft News - Read full article: http://www.airsoft2day.com/news/26-t...#ixzz250RyEqce


Hope this helps
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Old August 30th, 2012, 09:04   #3
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+ 1 for Fuji

You should take a look at this:

http://orga-airsoft.com/is-wider-better/

''The ORGA Magnus 6.23mm WideBore barrel increases accuracy and trajectory by reducing barrel friction and inner barrel bouncing. The width of the barrel ensures that hop-up spin is constant and consistent when it exits the barrel. This allows for precise, long range shooting, with 60-70 meter accuracy at under 1J.''

The combination of the inner barrel, Ho-up, bucking and nub is also important.
Good quality and matching component is the key.
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Old August 30th, 2012, 10:18   #4
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Those are some good reads. Here's what it boils down to...for me...after fiddling with things over the years.

First off, you need to keep the question at hand clear...and establish what you want to do really.

The primary effect that barrel length has on things is....the over all length of the gun. An MP5K can be made to shoot as hard as a M4....a VSR 10 can be made to shoot as soft as a springer pistol. So...re. barrel length...go with the length you need for your build, keeping the following in mind.
1. The barrel should remain centered in the outer barrel and not move for maximum accuracy...either by being a nice fit, using shims/tape/orings, etc...
2. That it be made to precise tolerances along it's entire length
3. Material selection should be made on performance vs. budget

So you can adjust your spring power/gears/motor/etc...in your build to deliver the speed/power that you want...and they should be matched to your barrel length for optimum performance and efficiency.

So here's a rephrase of your question (I think)...being a bit more specific:
Q. If I setup for the longer barrel length...what happens if I swap it for a shorter barrel without changing anything else?
A. Your FPS will drop. How much...it's hard to say, but say between a M4 barrel (363)and a shorter SIG552 (247) it might be 55-ish FPS. (I used to have a switch inner barrel setup that I could just drop a different hopup/inner into to use both for indoor and outdoor). As said...when you put a barrel in that is shorter than ideal, your bb will leave the barrel before the piston has finished it's forward stroke.

Q. If I setup for the shorter barrel length...what happens if I swap it for a longer barrel without changing anything else?
A. Theoretically (assuming the setup was super efficient)...your FPS will drop as the BB will still be in the barrel when the piston reaches it's most forward position and there'll be drag. In practice...the FPS will go up a bit until it gets to that drag point, because most setups are a little over powered anyways. What if you go full retard longer than the setup is made for (i.e. stick a 550mm barrel on a 3/4 port M4 setup)...you'll drop a lot of FPS. Might be 100+

Inner barrel diameter
What's the difference between a 6.03 vs. 6.01?
With a tighter bore...
+ velocity (how much? hard to tell but low of 5 and high of 15 usually)
- potential for jams (BB's are imperfect...dirt/dust/moisture is a factor)
+/- potential for more accuracy (usually the comparison is between old stock 6.08mm and 6.04-ish barrels)

It's really a balance between having enough space so there's a good cushion of air around the BB while it's carried down the bore...having an inner diameter matched such that the BB can stabilize...and accounting for the less than perfect reality of life.

6.04/6.03's...in a good setup...have always done the trick. To be honest though...I think more accuracy can be had by really consistent compression, a good hopup rubber and a matched barrel length...than sweating 0.02-0.04mm in the barrel diameter. There is absolutely no benefit to a tightbore if you're running a crappy stock hopup rubber with a leaky system.

Just my $0.02...don't sweat it too much. Just buy a good brand with a length to match your build...and match the cylinder/compression parts to suit that. Compare with some other brands on the barrel lengths...they're not all the same. Don't sweat 3-5mm difference...won't matter.
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Old August 30th, 2012, 10:46   #5
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Unconvincing...

Quote:
Originally Posted by Warlock View Post
+ 1 for Fuji

You should take a look at this:

http://orga-airsoft.com/is-wider-better/

''The ORGA Magnus 6.23mm WideBore barrel increases accuracy and trajectory by reducing barrel friction and inner barrel bouncing. The width of the barrel ensures that hop-up spin is constant and consistent when it exits the barrel. This allows for precise, long range shooting, with 60-70 meter accuracy at under 1J.''

The combination of the inner barrel, Ho-up, bucking and nub is also important.
Good quality and matching component is the key.
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Old August 30th, 2012, 10:58   #6
highny
 
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Thanks for all the help and tips but I can't help to feel that air volume is very important in this case. Instead of spending a large amount of cash on trial an error, could I simply calculate the cylinder air volume and the volume of air from end to end of the tight bore to find that perfect number? Would the consideration of bb weight come in play in this case?
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Old August 30th, 2012, 11:17   #7
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as long as you're not on the threshold, generally you don't have to... as long as the cylinder is matched to range of barrel lengths, you don't have to do much hardcore calculating.

My research has noted that 6.03s perform much better than 6.01s

Though my upgrade philosophy is to correct the compression variance first... fix it so your gun shoots as close to the same fps as possible on every single shot. Your consistency in accuracy goes up as a result. Adding a longer barrel to that is the last thing to do.
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Old August 30th, 2012, 12:30   #8
m102404
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If you want to go through that you could. But the system isn't a perfect one (i.e. as if you were to take one piston/syringe of a given diameter and hooked it up air/water tight to another one of a different diameter). There are a lot of variables with each setup...and no setup will ever be perfect.

For example, losses of efficiency will be:
- leaks in the piston head, nozzle, hopup rubber
- leaks around the BB (it's obviously not like a bullet that will form/impress to the barrel)
- resistance from the hopup application
- etc...

And in your calcs you'd need to anticipate the action and delivery of energy from the spring as it expands. The piston is accelerating from a stop to a stop...and the projectile starts to move before the piston is at full speed and is out the barrel before the piston comes to a full stop. I'm no math wiz...that sounds hard to calculate.

What I was trying to say is...don't sweat the "ideal" setup...because it'll never happen. Set it up so that there's more than enough air going down the tube (and manufacturers have already done that with the cylinder ports/barrel lengths)...and adjust muzzle FPS/power with your spring.

BB Weights
Spring powered systems are not a "compressed air" system. Air is not compressed and then released instantaneously. It's inherently a leaky system...the compression parts leak, the projectile does not seal with the barrel. The volume of air in a cylinder is not appreciably compressed when the piston goes forward...there's just a moment of restriction as the BB passes the hopup and then it's simply pushed along until it's speed matches that of the speed of the air moving down the barrel...or it runs out of barrel. A heavier BB is not brought up to air speed as quickly as a lighter one.

As MadMax so eloquently put together in another post...the purpose of the porting in a cylinder is not to reduce the amount of air, but rather to allow some "run up" time for the piston to get up to speed before the BB starts to move.

A great practical example of this is to put a full cylinder and a short (say MP5K) barrel together. You'll get very low FPS' because the BB's out of the barrel before the piston gets up to speed. You'd have to put a retardedly strong spring in there to get any decent speed out of it. Swap that barrel for an AK length and you're back in business.

While much of the parts/pieces are the same with a gas based system...the power source is very different. The liquified gas expands at a rate and the longer/more space it has it will continue to expand. Since the resevoir of liquid gas is "plentiful" for a given shot...the potential expansion is more than sufficient for it to apply power for any barrel length.

Take a gas setup and shoot a given weight of BB through a given barrel length...then swap just the barrel for a longer one. Your FPS will increase...because more gas has been allowed to expand longer. Swap it for a tighter barrel...your FPS will increase...because there is less leakage around the BB.

Take a gas setup and shoot one weight of BB through it. Then swap for a heavier BB. If your barrel length is sufficiently long...your FPS will remain the same....the power of the shot will go up though. Then swap for a lighter BB...again, if your barrel length is long enough...the FPS will stay the same and the power level will go down. You can start to see this effect in "full size" GBB pistols that have tightbores...it's very noticeable in GBBR's, especially those based on the negative pressure system.

If all that sounds like too much bother...you're right, it really is. Just skip back to the italicized part
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Old August 30th, 2012, 13:56   #9
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Quote:
Originally Posted by Blackthorne View Post
Unconvincing...
Do your homework and search ''ORGA Magnus'' in Google.

A lot of positive feedback.

60-70 meters accuracy at only 1 joules is very good. some are prentending 300-350 ft accuracy on snipers at 500 fps with this barrel.

I might give it a try lately.

Systema came up in 2012 on their revolution PTW with a new taper inner barrel design ranging from 6.03 to 6.05 bore diameter. They are saying that a larger bore at the exit of the barrel increase the accuracy and range by stabilizing the BB and preventing it to touch the inside of the barrel for a more consitent and effective backspin. They first try 6.1mm and after further testing they came up with this solution.

Longer barrel will only slow you down.
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Old August 30th, 2012, 15:14   #10
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...but i remember vaguely in past that Marui and some of the more venerable airsoft manufacturers said that the bb does acutally touch the innards of the inner barrel. IIRC, near the exit where the Initial force of the compressed air is more dispursed and the bb loses some of the cushioning and results in a "bouncing effect"

Perhaps this may be speculation and i am sure everyone will contend. And I am sure to get flamed for that one.

Dont know about present times but just throwing it out there.
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Old August 30th, 2012, 15:53   #11
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I did my homework man, think about what I do for a living for a second..

The responses to scientific question on their site are weak, often "referred to the engineer" and then not responded to at all.

For every 500 they have saying it's great I can give you 5000 that say a 590 mm 6.01 works great as well including me . I had on for years that delivered the results they claim.

Of course I am also betting that BB's don't actually touch the inside of the barrel at all during trip down the barrel (we have a bet going at Bastard Labs). We will be testing this this fall.

But even if it turns out it does, I see no reason why it would bounce in a small barrel and not in a large barrel. If the BB has a natural tendency to smack off the sides of the barrel in transit, why will that stop just because it's given more room?

Makes zero sense, especially from a fluid dynamics perspective.

Quote:
Originally Posted by Warlock View Post
Do your homework and search ''ORGA Magnus'' in Google.

A lot of positive feedback.

60-70 meters accuracy at only 1 joules is very good. some are prentending 300-350 ft accuracy on snipers at 500 fps with this barrel.

I might give it a try lately.

Systema came up in 2012 on their revolution PTW with a new taper inner barrel design ranging from 6.03 to 6.05 bore diameter. They are saying that a larger bore at the exit of the barrel increase the accuracy and range by stabilizing the BB and preventing it to touch the inside of the barrel for a more consitent and effective backspin. They first try 6.1mm and after further testing they came up with this solution.


Quote:
Originally Posted by Warlock View Post
Longer barrel will only slow you down.
In every other application on earth (rifles, blow guns) longer gives more time under pressure and more stability. I have seen nothing convincing other than the PR on their website to convince me otherwise.
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Old August 30th, 2012, 16:30   #12
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Here's what matters
consistency of the bore (not size)
parallelism of the barrel (not length)
quality of your hop rubber
compression of your mechbox and the seal between air nozzle and hop rubber
And having the proper weight BB for your FPS

Accuracy and range is about having laminar, and constant pressure airflow behind the BB. And making sure that BB is at it's nominal relative velocity.
A 350fps gun with good seal will outrange a 470fps gun with a poor seal
And a .3g BB will have more accuracy at 430fps than it will at 470fps

Barrel length makes incredibly little difference to range and accuracy. I've had a stock 6.08 brass barrel P.O.S. HFC beretta that could hit a torso at 200 feet.
My VSR has a 430mm barrel and it'll hit things accurately out to 260ft
And most importantly, friend of mine had a 650mm barrel in their VSR and actually was less accurate than I, due to running .3g BBs at too high velocity

In theory a longer barrel always gives you better accuracy. In truth, the BB is stabilized after just 80mm in most gas guns, much more in AEGs (due to less initial pressure).

I do agree that a tighter bore decreases the BB's ability to bounce due to creating a higher pressure zone around it, to better center the BB down the barrel. But you're thinking like an engineer, that theory only works in labs.
In the real world, barrels get soiled, sometimes very quickly. Larger bore means less chance of the BB hitting dirt down the barrel.

Remember guys, science is supposed to explain what happens in the field, not to argue against it.
Gas pistols (Like marui socom) get some pretty impressive range and accuracy for having 80mm barrels and at only 300fps.
My VSR at 430mm 6.03 bore will match any accuracy you can get out of a 650mm 6.01 barrel.

I don't know the details on the science, I just know how it works in the field.
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Old August 30th, 2012, 17:55   #13
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I've seen people with little to no practical gun tech work claim that a m16+ length inner barrels are the way to go. The individual ordered a custom EDGI 5.98mm ID, for a 24" Length barrel, (M16 Suppressed). The hopup/barrel system used performs no better than my 6.03mm ID, 415mm length system with the identical compression system behind it.

On some other more technical forums, the generally accepted "optimal" Inner barrel length is somewhere between 415-455mm given what we have available for springs, and cylinders.

Unconvinced/skeptical is my response to this orga barrel. If they phrased it that the relationship between the ID and the diameter of the BB is the key factor, I could be convinced.

Out of curiosity I never really looked into this but what are the Diameters of 8mm barrels (standard) and "upgraded". and what is the standardized diameter of a 8mm bb (7.95mm??)


EDIT:
I have also noted that a 1.7j gun shooting 0.30 BB's can outperform (range) a 3.7 j gun shooting the same ammo, however when you move the ammo weight to 0.66g you do get a marked improvement in the 3.7j guns.
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Last edited by Azathoth; August 30th, 2012 at 18:01..
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Old August 31st, 2012, 00:21   #14
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Exactly, gotta match the weight to the speed
The cap for .3s is around 440fps, then you need .36s
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Old August 31st, 2012, 08:20   #15
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I apologize a tiny for hijacking but its somewhat relevant to the topic at hand.
I have a KA p90. bone stock, it chrono'd at 380fps with .2
I swapped to a 6.03 450mm element (I know...) and it still chrono'd at 380fps at Rock the Ridge 2.
Then I swapped to an A+ demon hop up rubber and prowin aluminum hop up unit with the same 450 barrel. FPS is all over the place. some shots were around 350, some were 280, some as low as 190. I didn't touch the gear box or the cylinder.

So then I got rid of the prowin hop up and tried the a+ hop up rubber only and it was still being really inconsistent.

I am using .25g BB bastards so I know the BBs can't be at fault. And the barrel is clean. Any idea what could be causing such major variances?
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