Abbot
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Duck season...
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Post by Abbot on Jul 17, 2013 11:58:03 GMT -5
I'm looking into getting a TBB (6.03) for my MK18 Mod1, but I'm not sure what legnth. I will be putting a QD supressor, so it'll go through that, but what legnth should I put? The barrel is about 10", and the supressor is about 7", which would make about 431.8mm. But, naturally, I don't want the TBB to be coming right to the edge of by supressor, maybe an inch or two back.
I know there's the 363mm for the standard M4, but there's also a 390mm and 407mm (I'm talking abut the standard sizes), so out of those three, which would be best for a MK18 with a supressor?
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Gabriel
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The face of a man who has seen the Ancient Ones is forever twisted by the memory.
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Post by Gabriel on Jul 17, 2013 12:18:38 GMT -5
I threw a 247 mm in mine. Trust me, you will be taking off the suppressor a lot. Get a Madbull or Prommy one. If you are dead set on getting a longer one, get a 363mm. It will be about 1.5-2 inches shorter then the end of your suppressor.
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Abbot
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Duck season...
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Post by Abbot on Jul 17, 2013 13:12:56 GMT -5
My problem is that I'm playing outdoors a lot with guys using G3s, AKs and such, completely outranging me. That's why I wanted one pretty long. Would a 247 range, or outrange an AK's (stock) 447mm, or a G3's?
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Deuce
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Post by Deuce on Jul 17, 2013 13:15:34 GMT -5
I'm getting a 407mm 6.01 in my mk18, it will give me the range and accuracy that I'm looking to get out of my gun. Plus I don't mind longer guns in close quarters, minded its not even that long.
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Post by Gimpalong on Jul 17, 2013 14:05:10 GMT -5
Abbot,
barrel length does not impact range.
Range is a product of the velocity at which your rifle is shooting and your hop-up unit and its associated components (bucking, nub).
For example, a rifle shooting 300 fps through a 500mm barrel will throw a BB just as far as a rifle shooting 300fps through a 200mm barrel. Obviously, in the "real world" you're going to have some variation in range from platforms firing the exact same velocity - but it shouldn't be a radical variation unless you're running an r-hop or have made some serious modifications to your hop-up unit.
If you're being outranged you need to increase the velocity of your rifle and/or service your hop-up unit so that you're getting better range.
That said, I would go for a 247mm or 300mm barrel since it would come to the end of your outer barrel and still allow you to use the rifle with the suppressor removed.
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Deuce
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Post by Deuce on Jul 17, 2013 18:32:40 GMT -5
@gimpalong you are right that it will not affect range (to an extent), but it will help your accuracy. All of my guns are accurate up to a certain distances and all have different length barrels.
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Gabriel
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The face of a man who has seen the Ancient Ones is forever twisted by the memory.
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Post by Gabriel on Jul 17, 2013 19:24:58 GMT -5
Dude, my 247 6.01 is shooting like a laser. My range isn't very good, but that's due to my god awful compression.
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Post by sneakytiger on Jul 17, 2013 22:37:47 GMT -5
I get over 250' of usable range out of a 280mm barrel and a completely custom setup. Accuracy is great at that distance as well. If your looking for range and accuracy, you'll get more out of an r-hop and bioval .3g bb's than any barrel or other customization.
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Abbot
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Duck season...
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Post by Abbot on Jul 18, 2013 15:10:30 GMT -5
So if my friend is using a stock JG G3 (about 6.08mm), he is outranging me due to his stronger spring, and not his longer barrel, correct? Also, heavier bbs means farther range, but lower FPS, correct? So .3 bbs would outrange .25s? What the bleedin' devil is an R-hop? Any vouches for the REAPS Bucking?
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Post by Gimpalong on Jul 18, 2013 15:41:23 GMT -5
Abbot, First, I want to preference this by saying that I don't know that much about airsoft physics (so I might be getting this stuff wrong) and that there are many other folks who know more. A lot of them on Airsoft Mechanics. Range is a product of energy output. So, if your buddy is shooting at, say, 400 FPS with .20s and you're shooting at 300 FPS with .20s, he's going to out range you no matter what barrel length you or he are using. If you use this calculator (scroll down), you'll be able to get some very rough numbers on how far a BB will travel if it is shot at a specific FPS. Remember, this is in a perfect world. These figures are based on math, physics, gravity, etc. So, according to the calculator: A .20 BB at 300 FPS (.84 joules) will travel, approximately, 135 ft, while a .20 BB at 400 FPS (1.49 joules) will travel, approximately, 180 ft. That's an extra 45 ft of range for the person firing at 400 FPS. Heavier BBs, depending on the initial FPS at which they are fired, may give you slightly more range. This has a lot to do with how the BB interacts with the hop-up unit. So, at 400 FPS, a .25 BB might go further than a .20 BB because the .25 is "hopped" more effectively than the .20 BB and retains energy longer as it travels through the air. However, the idea that a heavier BB will ALWAYS travel further than a lighter BB is false. If you fire a .40 at 1 joule and a .20 at 1 joule, the .20 will go further. If you're firing BBs at 1.5 joules (for example), you're going to experience some diminishing returns as you increase BB weight. How your hop-up unit interacts with various BBs at different weight plays a big role. A .20 might fly a long way, and a .25 might fly even further, but a .30 might fly less far than a .20 and a .40 might fly less far than the .30. How much range you will get out of a gun depends on the initial velocity at which the gun is firing the BB, the weight of the BB itself and the hop-up unit and its associated components (hop-up bucking and nub) According to the calculator that I linked to above: .40 BB @ 1 joule = 232 FPS = 104 ft traveled .25 BB @ 1 joule = 293 FPS = 132 ft traveled .20 BB @ 1 joule = 328 FPS = 148 ft traveled The above calculation is, again, based on a perfect world and doesn't take into account the effect of a hop-up unit. It seems pretty a fair bet to say that the .40 will not go as far as the .20, but the .25, given the right combination of hop-up, might actually travel further than the .20. Remember, your hop-up matters. It certainly matters more than your barrel when it comes to range. To directly answer your questions: Sort of. If two BBs of different weight are shot at the same energy, the heavier BB will be traveling slower through the air (i.e. it will be traveling at fewer FPS). The heavier BB may OR MAY NOT travel further. Again, it depends on initial energy applied, and the difference in BB weights. Ghast will explain. It's basically a fancy, custom-fitted hop-up bucking/nub that applies hop-up in a more efficient (?) way which results in the BB being "thrown" further. Or you can search on Airsoft MechanicsReviews of the REAPS have not been super positive from what I have seen. Check this review on Arnie's or search on ASM. Hope that helps! Good luck!
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ctres
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Post by ctres on Jul 18, 2013 15:49:45 GMT -5
A longer barrel when matched with the proper volumed cylinder can sometimes give the bb more time to accelerate and hence a higher velocity than a shorter barrel with the equivalent spring. The length of the barrel itself does not give the bb more range, the extra range is more of a byproduct of the extra fps. If you want the extra fps, just get a little bit stronger spring as long as your other parts can handle it.
As far as accuracy goes, some people speculate that the optimum range is in the mid 400mm length, but this is not documented in any way, and to do so would take a lot of investment in parts as well as a perfect testing area and equipment to document the process. The overwhelming consensus in the tech community is that quality of the barrel in terms of bore surface finish, bore diameter consistency, roundness, straightness and resistance to corrosion are far more important to barrel performance than merely bore diameter and length. It is generally accepted that in comparison to most other brands out there prometheus stainless steel barrels excel in pretty much all of the above catagories.
Aside from the barrel itself, the hop up is at least, if not more, important than the barrel. The hop up is what gives the bb its range so it is crucial that it be as consistent as possible. The r hop is a concave piece of rubber like material that is shaped by the used to precisely fit the window of the barrel where a normal mound from the bucking would protrude. It is used in conjuction with a mouldless bucking and a flat hop up nub. The r hop provides a much extended but more gentle point of contact with the bb when compared to a normal bucking and nub. There are a couple theories of how it works, but no conclusive evidence. Regardless, it often drastically improves range when used with heavy bbs. The r hop was designed by hunterseeker5 of airsoftmechanics and is sold under his branding.
Aside from all that, air seal is vital to consistency and accuracy. If you have air leaks, which is pretty much a given for all stock guns and probably a lot of "upgraded" guns as well, then you will lose both accuracy and velocity.
You will find a ton of useful stuff on airsoftmechanics if you search around and read the stickies. I advise you to not post questions right away so as to avoid be flamed for looking like a noob. ASM doesn't take too kindly to spoon feeding.
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Gabriel
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The face of a man who has seen the Ancient Ones is forever twisted by the memory.
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Post by Gabriel on Jul 18, 2013 17:22:35 GMT -5
I have heard form several people that with a V2 gearbox, a 363mm by 6.03mm is the best length/ diameter. I heard it has to do with the ratio of Cylinder to barrel volume being 1.7 times greater. Do you know if that's true?
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ctres
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Post by ctres on Jul 18, 2013 19:30:23 GMT -5
Cylinder to barrel volume changes depending on what weight bb you are using. As the piston moves forward the air in the cylinder actually compresses before the bb begins to move. Once the bb's inertia is overcome and it begins to move the air is pushed out through the barrel. The more mass the bb has, the more inertia it has, so the air in the cylinder will compress more than it would with a lighter bb, hence a greater cylinder to barrel volume is needed.
Ideally you would pick one weight of bb that you will always be using. You then start with an overvolumed cylinder and begin extending the port via dremmel or whatever in very small increments. Every few mm reassmble and chrono. You would keep extending until the velocity stops increasing or drops off slightly. The issue with this is that it is very time consuming and there is a lot of room for error when reassembling. In order for anything to be relevant you have to keep every part constant and you must already have perfect compression. Of course there are other factors such as spring design and piston weight that can change things as well, so there is no realistic way to come up with an equation, and changing parts down the road could throw off your gains. The moral os that just because someone spews what supposed ratio worked in his given setup it may not work for you. An accurate experiment would require lotsnof money and ideal testing scenarios. In order for any results to be conclusive everything else must remain totally constant.
The whole volume matching thing is really not something that most people should even worry about IMO, I haven't even played with it myself, everything above is just information I've collected on it after following discussion of the idea for several years. You really have to be at a point where everything else on your gun is 100% perfect, and honestly I am not to that point with my primary build. If you are interested in some semi conclusive results, check out noobie's thread on it on airsoft retreat.
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Post by slippy on Jul 18, 2013 20:01:31 GMT -5
A simple way, to my understanding, to have proper cylinder to barrel volume is to not change your stock barrel length. As was discussed before, a bigger spring gets you more velocity. A good bucking, hop up and quality tb will increase your usable accuracy. From what I've heard r-hop's do wonders as well.
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Post by Shadow (314) on Jul 18, 2013 20:32:14 GMT -5
I'd like to weigh in here. I'm interpreting what you want to be as an increase in EFFECTIVE range. To me, that means being able to reach out and touch someone consistently from farther away. To this, I would say mere increase in muzzle velocity may or may not be the answer. What you need first is consistency. If you know exactly where each shot is going to go because you're rifle performs the exact same every time, then to increase distance of the BB traveled, you can only angle the muzzle upward and your impact point will be predictable. Now, basic ballistics would tell us that this only can go so far since there is an optimal angle to which you can fire a projective for maximum range. After you can achieve consistency and be able to call your shots, then you can add additional force to have a longer shot. (My personal opinion is that the best way to do this is make sure your air seals are all at 100% efficiency and all the power is going behind your BB) Another variable in airsoft is the backspin of the BB we call hop up. Again, tweaking the hop up just right and making it consistent will go a long way. I always tell people that a good bucking and nub will be the best bang for your buck. After that we have the projectile itself. A heavier BB will have greater inertia to all directions other than toward it's target to not be forced off it's original path by wind, leaves, and other forces other than gravity, which is predictable. Also, since we're firing spinning spheres, having a balanced projectile makes a huge difference as well as the surface aerodynamics of the BB. Yes, a heavier and higher quality BB will slow down your shot and limit your overall range, BUT it may also increase your effective range. And that's what really matters. So, in effect, I would recommend you focus on consistency before accuracy and don't worry about your FPS yet because if your rifle can shoot 450 FPS but you'll never be able to aim that BB's spread after 150 feet, what's the point?
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