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Old October 10th, 2013, 10:08   #1
paulwes83
 
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Inner barrel question

Hey guys,

I recently read that that...

tighter inner barrel=increased fps, but wider grouping
looser inner barrel=decreased fps, but tighter grouping

My question is, why would anyone want a tightbore barrel if it decreases your accuracy?

Or are those findings listed above, pretty negligable in that the fps decrease/increase won't be significant and the accuracy won't really matter unless you're a "sport" airsoft shooter who does competitions?

I'm looking at this from a combat perspective and can't see why you'd ever want a tightbore barrel when you can always up your FPS enough with springs, internal component weight, etc. Accuracy would be more important given the usual FPS limits on fields, no?

Thanks all
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Old October 10th, 2013, 10:09   #2
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Is money really the deciding factor on a tightbore, i.e. it's cheaper to get a tightbore barrel than upgrade internals?
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Old October 10th, 2013, 10:23   #3
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Increasing your muzzle energy via spring alone is incredibly inefficient. Imagine a inefficient compression system with a M150 spring, and air leaks everywhere. Contrast to a lighter spring M120 which and no air leaks. The increase in efficiency means reduces wear on components and better battery life. More reliability is always a good thing.

As for the tightbore question. It depends on the bore in question. Just because the inner diameter is smaller doesnt make it a more accurate barrel. Straightness, smoothness of finish, inner play a role.

For years and years the thought has been that tightbore prevent BB's from rattling along the inner edges of a stock barrel which at the time was between 6.08-6.12mm. Nowadays bore are coming stock 6.04-6.06 which has been the traditional tightbore range. For YEARS moving from stock barrels to tightbores have been advantageous and was supported by the player base. However, the tighter the bore the more likely that debris/dust will cause fouling, and after "X" rounds you will need to clean your bore or it will not be performing as it should be.

About 3 years back a bunch of people Japan/phillipines theorized that it's not the bore diameter that mattered but the relationship between BB diameter and the bore. Hence the early widebores came about. You can read on their websites regarding the theory but in a wide bore debris is not as big a factor.

TL;DR
Stock to Tightbore = generally higher FPS, better groupings than stock
Stock to Widebore = Generally lower FPS, better groupings than stock.
Tight to wide = lower fps, Typically better range 15-20ft, wider groupings from my limited experience.

Tested on PTW, i can hit a dinner plate sized group at ~250ft with the PDI tightbore. With the widebore I can hit a 6-8ft sized grouping at 270. at 250ft I get a 4ft sized group, With stock systema barrel 2011, I can hit a man sized group at 250ft
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Old October 10th, 2013, 10:30   #4
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Companies manufacturing tightbore barrels use marketing tools to advertise that tighbore barrels increase accuracy. It's mostly true but not for the fact that the bore diameter is reduced but because different materials are used and bore consistency is improved. But of course, they can't exactly advertise the fact that the same effect could be achieved via barrel lapping because who would buy their barrels? Also, psychologically-speaking - would you be more inclined to purchase a barrel of the exact same bore as the one you are replacing with the promise that it will improve accuracy or would you purchase something that's quantifiably better ("0.05mm tighter bore!"). Then there's the notion that precision fitment and tightness somehow translates to accuracy coupled with the fact you're dealing with essentially firearms enthusiasts who naturally reason that somehow real steel ballistics apply to a spherical object when in fact the axes of spin are completely different. But hey! Milsim, right?

Then there's the FPS-junkies whose sole intent is to get as close to the mythical 400fps limit as possible and they've read somewhere that adding a tightbore barrel will boost their FPS by 30-40. Again, this isn't as much to do with the bore diameter restriction than the fact that most people change hop-up rubbers/units and/or perform some sort of hop-up mod in addition to adding the barrel which has a side benefit of creating a better air seal - something that should have existed in the first place.

The point of recovering lost FPS by using a "widebore" barrel - while valid, is not widely accepted by most because it involves performing mechbox modifications. Simply put - it's easier and faster to install a barrel than to swap a spring and to quantifiably identify the improvement via a barrel upgrade. Also, despite what their internals can actually handle, most players are not keen to add additional stress to their mechbox to recover that lost FPS.

You add all of that together and you can begin to understand why "tightbore barrels" are so popular.

Compound all of this with the fact that you're dealing with different hop-up technologies which change the way the BB rides over the hop-up bump, how the ammo is fed, etc.

Last edited by Stealth; October 10th, 2013 at 11:32..
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Old October 10th, 2013, 11:29   #5
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The term "tightbore" doesn't necessarily MEAN tightbore anymore. We just use it to describe an upgraded barrel.
Stock barrels are typically 6.08
"tightbores" are 6.01 to 6.05
"widebores" 6.08 to 6.23

The trick is the balance. A 6.01 and 6.08 barrel have the same potential for accuracy.
It happens that the 6.01 is more often manufactured to way better standards than a 6.08.
Problem is the 6.01 is going to foul very quickly and affect your accuracy after just one mag.
But a wider bore needs a stronger spring due to the air loss around the BB. Going from a 6.04 to a 6.10 I lost about 30fps on the PTW.

The BB doesn't actually ride the barrel like a bullet in a rifle barrel. It rides a cushion of air centering it down the barrel. So the actual diameter of the barrel is not critical, within reason, what matters is the quality, consistency, and concentricity of the barrel.

Orga makes a 6.10mm barrel for PTWs, and they come damn close to being on par with the new evo 6.04 barrels, and the 6.10 outperforms some other 6.03 and 6.05 barrels.

Barrel quality is more important than barrel diameter
And the tighter the barrel, the faster your accuracy will drop off.
With a 6.03 in my bolt action rifle, I noticed accuracy loss after just 130 rounds, it's not significant loss, but it's enough to be a huge pain as a marksman.
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Old October 10th, 2013, 14:14   #6
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Would a bore-up kit be suffient to compensate for the loss in FPS from a larger bore barrel, provided the larger bore is of good quality and uniformity?
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Old October 10th, 2013, 14:22   #7
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how long and tight of a barrel are we talking here? a full cylinder can push enough air for a 600mm barrel.
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Old October 10th, 2013, 15:40   #8
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I'm looking for more of a general rule with the larger bore barrels, but I'm not sure if there is a general rule for achieving good accuracy because it would all depend on barrel length.

Also, I've been told that a standard cylinders can only handle up to 500mm.

Quote:
Originally Posted by lurkingknight View Post
how long and tight of a barrel are we talking here? a full cylinder can push enough air for a 600mm barrel.

Last edited by paulwes83; October 10th, 2013 at 15:52..
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Old October 10th, 2013, 16:28   #9
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Quote:
Originally Posted by paulwes83 View Post

My question is, why would anyone want a tightbore barrel if it decreases your accuracy?
I don't know about that. I noticed a considerable improvement on accuracy with my G36 after purchasing a tightbore, however, that could have just been from superior quality.

I DO know, that good accuracy is the job of the Hop-up more than the barrel. When you pair a good hop, with a good barrel, it can be magical.
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Old October 10th, 2013, 17:25   #10
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Quote:
Originally Posted by lurkingknight View Post
how long and tight of a barrel are we talking here? a full cylinder can push enough air for a 600mm barrel.
Might be able to step up cylinder size if you have a ported cylinder and switch to a widebore. All I know is with a PTW, same barrel length, in a wide bore, 30fps loss.
Without thinking about it too hard, having extra volume might help, but it's not a volume problem so much as an air leak problem. More air escapes around the BB.

Quote:
Originally Posted by paulwes83 View Post
but I'm not sure if there is a general rule for achieving good accuracy because it would all depend on barrel length.
This is not real steel. Barrel lengths beyond a certain length mean absolutely nothing.
Ever wonder how it was possible that a stock GBB pistol with a 4" barrel could match the range and accuracy of a stock M16 AEG?
Once the BB has centered itself in the barrel, it's centered. And no extra length of barrel is ever going to get it any more centered than it already is.

Amos and I built twin VSR-10s, he had a 650mm barrel and I had a 380mm barrel, and our accuracy was exactly the same.

With R-hop, due to it putting less pressure on the BB, people have said as short as 247mm can have fantastic accuracy.

And on PTW's there are plenty of reviews of people having better range and accuracy with 10" CQB barrels over 14.5" M4 barrels.
Just as well, systema does not make a 20" M16 length barrel because of this. All their M16s come with 14.5" barrels.

The ONLY things that matter in range and accuracy are this;
mechbox compression
hopup quality and seal
barrel quality, not necessarily bore, and length really doesn't matter beyond 420mm, shorter with Rhop
BB quality
and that you use the proper weighted BB for your fps range
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Old October 10th, 2013, 17:47   #11
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Quote:
Originally Posted by paulwes83 View Post
Would a bore-up kit be suffient to compensate for the loss in FPS from a larger bore barrel, provided the larger bore is of good quality and uniformity?
You cannot successfully use a bore-up kit without the use of a spring that as at the very bare minimum, equal in strength to a Systema M120S (~420fps) or higher. Otherwise, you will actually lose additional power.



I've mentioned this theory lately, that:

Tighter bores = higher FPS, but reduced grouping tightness
vs
Wider bores = lower FPS, but tighter groupings.

Granted, this theory did not come out of nowhere. There are multiple very large barrel manufacturers which attest to this - the first of which, was Systema around 15 years ago, who was also the FIRST mass produced aftermarket manufacturer on the market. Their 6.04mm barrel still remains as one of the highest selling "tightbore" barrels available. (There are other factors at play in regards to this, based on market demographic, business aspects and such, which I'll leave out of this discussion.) Playing with many bore says, they came to the conclusion, that 6.04mm was the "perfect" compromise of power and accuracy.

KM/Head1950 quickly followed suit with their release of a TN coated brass barrel, also using a 6.04mm bore. The inclusion of the TN coating yielded a longer lasting finish, as well as self-lubricating properties to reduce friction, reduced oxidation, and ease of cleaning.

PDI shortly followed suit with the release of three barrels to reach the needs of a larger audience. Some users wanted tighter bores for higher power, whereas others were willing to sacrifice some power for tighter groupings by sticking with a stock bore. Using higher end manufacturing techniques for greater concentric tolerance and higher quality materials (Japanese grade stainless steel), PDI created the first line of inner barrels which proved these theories. They hit the market with all three bores at the same time: 6.08mm, 6.05mm, and 6.01mm. In their opinion, and possibly to set themselves apart from the competition, 6.05mm was determined to be the "perfect" bore compromise of both power and accuracy. They openly advertised that the 6.08mm bore had the greatest "carry" and least power of the three bores, whereas the 6.01mm had the least "carry" but highest power output of the three. The 6.05mm was placed squarely in the middle. This was the first great proof to the theory, as they effectively eliminated ALL OTHER VARIABLES, including manufacturing tolerance, coating(s) (or lack thereof), manufacturing techniques, length, crowning methods, window dimensions, etc. The ONLY difference between these three barrels, were the inner bore, and by extension, the wall thickness.

I saw PDI's marketing materials on this as early as 2004. It may have been around even before that. Systema and KM were out before I came in to the scene in 2001, so I don't know the timeline on those products.

Laylax came back with their own argument that refuted PDI's claim that 6.05 was the perfect bore. After all, who is PDI to say what the best compromise was? For the Japanese market, most of their engagements were very short to medium length engagements, and thus, Laylax concluded that their customer base was willing to sacrifice a bit more accuracy, for power efficiency. Thus, Laylax produced 6.03 bore barrels under the names Prometheus for their AEG line, and Nine Ball for their pistol/SMG lines.

In my opinion, from 6.03mm to 6.04mm, and from 6.04mm to 6.05mm, the differences in power and accuracy are so minimal, that it would be negligible. This forms my opinion that these companies are doing this simply to set themselves apart from their direct competition.

It's my own personal belief that LayLax barrels (Prometheus, in particular) have become the most popular, simply because their offered manufacturing tolerances very close to PDI, a quality very close to PDI, at a significantly reduced price. PDI barrels, as nice as they are, carry a massive premium that many consumers simply cannot justify. As such, Prometheus has now grown to be one of the most popular tuner barrels.

Laylax hasn't ended there. Just recently, (in the past year) they've released Nine Ball 6.00 "POWER" Barrels, which do exactly as it claims. It produces more power, with the advertised caveat: wider groupings. Yet, another manufacturer removing all other variables and proving the theory.

This project has been in the works by Laylax for at least 2 years, as the theory was already causing extreme tuners in Asia to play with very extreme ends of the spectrum. Laylax just decided to take it to mass production.

Orga, at around the same as Laylax's release of their "Power" barrels, came out with their 6.13 and 6.23mm wide and ultra widebore barrels to take the extreme to the other end of the spectrum.

"The proof is in the pudding", as they say, as on paper, all of these claims are verifiable.

While I did not disbelieve these claims, I had to see it for my own eyes. Thus, I commissioned a custom barrel manufacturer to turn out a full range of short barrels to test this theory for myself. I went even further with the spectrum, and got barrels as tight as 5.98mm, all the way up to 6.23mm in increments of 0.01mm. A few less popular bores were left out of the order to save me cost (ie, 6.06, 6.07, 6.09, 6.11, 6.12, and everything from 6.14 to 6.22mm), and I've only done a very rough test between the two extremes of the spectrum so far. 5.98mm versus 6.23mm. The difference was noticeable.

On the initial test of the 5.98mm bore, the accuracy was crap. It was theorized that the extreme tight bore exaggerated any irregularities in the projectile and also in how straight the barrel was crowned. Any irregularities at such an extreme bore caused a lot of turbulence at the muzzle as the projectile was sharply introduced in to the atmosphere. Thus, a solution was created to soften this introduction of the projectile into the atmosphere, and it drastically improved the tightness of groupings. I cannot divulge much about this technology as it's still in the works, but let's just say it's functional, and combined with a few other technologies, ILLusion Kinetics is working on some extremely high end ultra tight bore barrels that will have groupings nearing the widest wide bores while retaining huge power gains.

With Hi-Capa 5.1 length (112.5mm) barrels, I tested these two bores, and noticed a 0.4Joule difference between the two. At a 100 foot indoor range, I was able to get a grouping of 11" with the 6.23mm bore, versus a 13" grouping with the 5.98mm bore, using Tokyo Marui Perfect Hit 0.28g BB's. This 2" grouping is dramatic, but purposely so, and was why I chose a short barrel platform to test this, as it would most likely exaggerate this theory. Also keep in mind, this result is with the newly revised 5.98mm bore, versus an otherwise normal 6.23mm bore barrel with your typical crater cut. The additional technology that these barrels have over standard barrels, is that these are bull barrels. The outer diameter of the walls are slightly larger than your typical barrel, with the purpose of reducing vibration introduced inaccuracies.

The proof is positive.

The next step is to minimize more variables in the tests, as well as to test all of the other bores to find out what MY perfect compromise would be in terms of grouping and power output. For what it's worth, with pistol use, I would rather go with the tightest bore for the drastically improved power efficiency, as the grouping difference for typical pistol engagements doesn't warrant the power loss to me. It might make a difference to you.

The next step in the theory, is to test with longer bores - particularly, with AEG's. Unfortunately, the cost of this is much higher, so whether I get to that stage or not is still up in the air.

Quote:
Originally Posted by paulwes83 View Post
I'm looking for more of a general rule with the larger bore barrels, but I'm not sure if there is a general rule for achieving good accuracy because it would all depend on barrel length.

Also, I've been told that a standard cylinders can only handle up to 500mm.
In my experience, standard bore cylinders are good up to 550m. Above that, you will need a widebore cylinder setup.

Last edited by ILLusion; October 10th, 2013 at 18:00..
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Old October 10th, 2013, 18:14   #12
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Originally Posted by ILLusion View Post
In my experience, standard bore cylinders are good up to 550m. Above that, you will need a widebore cylinder setup.
I'm doing 550mm fine with a full cylinder and sorbo pad, without a sorbo you could probably push to maybe 600mm. I think that depends a lot on the piston head/cylinder combination, because how quickly the o-ring makes the seal will make a big difference here.
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Old October 10th, 2013, 18:43   #13
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Originally Posted by pestobanana View Post
I'm doing 550mm fine with a full cylinder and sorbo pad, without a sorbo you could probably push to maybe 600mm. I think that depends a lot on the piston head/cylinder combination, because how quickly the o-ring makes the seal will make a big difference here.
I'm not saying you're wrong. It's very possible that the standard bore full cylinder is good to... I don't know, 570mm or whatever. Just pulling that number out of my head. Your statement reiterates my point. Your full cylinder setup is still good up to 550mm.

We just don't know exactly "where" between 550mm and 590mm the widebore cylinder is required, as there really aren't any available out there on the mass market.

Unless we test it at 1mm increments at every barrel bore, it's hard to determine the exact graph where the switchover is need to be made.

But my point still stands, at some point, above 550mm length, the switch needs to be made to a widebore cylinder. As well, this could be offset by tightening the barrel bore further to reduce the required air volume to get the projectile out of the barrel.

I once did a 6.04mm 590mm setup with a standard bore full length cylinder, with a Systema M120S spring, and it was hitting just under 400fps.
On full auto, it got as low as 360fps, so there's some barrel suck happening.

Once I installed a wide bore cylinder, I hit just over 420fps, which is what the M120S should be hitting. That velocity was maintained in full auto fire. This is where my assumption is made that widebore cylinders are required for barrels above 550mm.

Last edited by ILLusion; October 10th, 2013 at 18:49..
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Old October 10th, 2013, 22:16   #14
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The idea that a longer barrel has more accuracy comes from real steel, which the physics do not translate over. Like almost none of the physics.
And the idea that a tighter barrel gives tighter groupings is common misconception from people who just don't know any better.
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Old October 10th, 2013, 23:10   #15
Stealth
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Originally Posted by ThunderCactus View Post
The idea that a longer barrel has more accuracy comes from real steel
That theory doesn't hold true either for barrels past 16".
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