How an airsoft gun really works - the physics

[Hectic]

great write up, good place to send new players as opposed to blabbing at them for a half hour lol.
just a cpl things to ask/add.
ive been using 6.03-6.01's in my vsr10's with good results. Are u sayin i could get better results with a looser bore?
and seccond. My most recent inner in my vsr is a madbull 6.01, the coated type of barrel, tho im sure the coating will eventually become damaged, in a bolt action im sure thatll take quite some time, what are your thoughts on those?
lastly, i started using a high end car wax (mothers) to clean and treat my inners with good results, yes i clean em with soapy water or window cleaner, but then i run the wax through, let it dry, give a quick buff the apply a seccond coat, i find it leaves a nice smooth finnish and even removes/fills in minor scapes and blemishes, thoughts?

[Ricochet]

Wider bore are becoming popular again and seem to be having great success. Here's my issue with them and any other airsoft product. To me it's "all" about accuracy and distance, period. I want my gun to shoot as far and precise as possible, while still living within three parameters; the FPS limits of the fields I play, good quality 6mm BBs, and lastly the time it takes for my BB to arrive.

The best Airsoft barrels I have ever seen are the Prometheus 6.03mm for the Tokyo Marui VSR, and the Systema 6.04mm for their PTW, as well as variations of each. I have seen successful 6.00mm, 6.01mm, 6.02mm, but I've seen just as many or more that didn't work. The BB flight would become unstable and erratic. Theories here are that the bore is too tight and that the BB contacts the inside of the barrel too many times or it's disruptive to the hop-up spin, etc. But 6.04mm and 6.03mm are solid with great results. Most airsoft guns up until a few years back came stock with 6.08mm barrels, and even though some still do, many have gravitated towards the 6.04mm.

A gun is only as good as the sum of it's parts. Barrel, hop-up, nozzle, piston, gears, motor, etc. They all combine into what your gun is capable of. Precision pieces are not always enough, they must work with each other in harmony, as well as fit tighter properly. That is why certain systems have had great success. PTW is a good example. Every piece is machined perfectly and just clicks together. There's no play, no wiggle, and everything is high quality. We've all seen, or at least most of us, their superiority in action. If you were to lessen quality, lessen precision, etc, you will have negative effects on performance and longevity of the gun. So no matter how much you upgrade those parts, without all of those tolerances you won't have the same effect. Your gun has a maximum output level and although you can modify little things here and there, it'll never push past this performance.

Next and most forgotten is FPS limits. People conveniently forget this one when talking about distance and performance. "I one time saw a gun shoot this (--) far!" Is the equivalent of "my friend once caught a fish this (--) big". If you have the best, or one of the best guns that perform on a field, is there one out there performs significantly better? Sure there is, somewhere, but let's be frank. What were doing is projecting a 6mm BB down range, period. The physics here are what they are. I once saw a gun shoot a disgusting amount of distance, but its FPS was also ridiculously high for that time. Something like 750 FPS plus. It wasn't allowed to be fielded, and I can't recall it being especially accurate, but that BB sailed out of the barrel with zest, you bet you boots it did. Higher FPS only gives us one advantage, and that is you can use a heavier weight round, which are proven to have more stability for longer range. My 300 FPS pistol will not successfully launch a 0.30g round down range, just not enough power. I could try a more aggressive hop-up to help manage the weight, but really it needs a bigger push overall. Not to mention that too heavy of a BB travels excessively slow and if too slow can destabilize mid flight quite easily. There goes your accuracy, or your target just Matrix'd your BBs. So you want to use the heaviest weight BB your gun can shoot stable, that also doesn't arrive next week. So bumping up your FPS a bit can get you to that next weight, 0.28g, 0.30g, 0.32g, 0.36g, etc. You will likely "need" a very aggressive hop-up at this point though, and you're still stuck at your fields FPS limits, such as 400 FPS, etc. So if 400 FPS is the maximum, then you are stuck within that set of physical limitations, and that's that.

So onto wide-bore barrels. We've established the basic properties of quality parts, BB weights, Velocity, etc, and now your gun is already to go. So here's my three issues with going wide bore. Firstly you have to bump up your FPS to compensate. Due to the width of the inner bore either your air cushion doesn't have the same effect or it's able to escape forward past the BB at a greater rate. So you have to up your FPS to push the same BBs down the tube. This puts more stress over all on your gun because you'll need a bigger spring. What you can do with an M110 spring and a 6.04mm barrel, you'll need a M130 to do with a 6.10mm barrel. Secondly I'm not seeing difference in overall performance. I have seen some wide bores work wonderfully in some platforms, but not really out shooting or more accurately shooting than tighter bores with other combinations, necessarily. Third is that like most other barrel technology, we just don't know for sure.

Airsofters have been monkeying around with the physics of guns forever. Don't get me wrong, this is how things improve, but many times we change something with little to no effect, and then the fad dies out. My theory is this; if a barrel has the ability to hold a stable air cushion and is of high quality, it shouldn't matter which bore you use. Just like tighter bore increase your FPS, wider bore decreases it. So we've seen really tight bore barrels cause destabilization, not always, but it does happen. We're using 6mm BBs that actually, and usually will measure more closely to 5.70 - 5.90 if you want to get out the micrometer and measure thousands of them. This means if your barrel is too tight, then it's just too tight. Low quality BBs have actually been known to fluctuate in size more wildly and even be too big. You can see the issues with using 6.00mm BB in a 6.00mm barrel then. Also it may scrape, run, bounce, or contact the barrel all the way out causing destabilization in flight. There have been some successful cases of 6.01mm or other tight bore barrels being used, but usually in shorter barrels. Perhaps the short length helps stop the BB from bobbing around before it leaves the gun. Who knows? What I can tell you is that at a certain bore, it doesn't seem to matter. For instance at 6.04mm a short or long barrel can be used in any platform with success. Of course that's as long as the right parts, hop-up, and BBs are used. So realistically once you find a stable bore size such as 6.04mm, why go bigger? As long as the you have a stable air cushion, the right hop-up and rounds, what's the difference? I'll tell you again. The wider you go, the more FPS you need for compensation, meaning a bigger spring or more gas, just to get your gun to where it'll meet field limits and handle heavier rounds. At the end of the day a 6.04mm shooting a 0.25g round, with a M110 spring is about the same performance as 6.10mm shooting a 0.25g round, with an M130 spring. All we've done is increased pressure on our whole system to run that tighter bore.

Like I said, it all comes down to how far and straight your gun shoots, period. If you don't get an increase in overall range and accuracy, the. You've accomplished nothing. And in order for some technology to be considered legit it had to work better across the board. I have seen some airsoft guns beat up, broken, duct taped together, with low grade crappy parts in them shoot just fine. But for every one of those, there's a million that fail.

So what are the possible benefits of a wide bore? Well "in theory" you could run longer barrels more successfully because you lessened the chance of barrel fouling. More room could mean a smoother transition. Another is BB weight could make a difference. Having issues getting that 0.32g BB to fly nicely out of your gun? A wider bore, with a good hop-up, and the appropriate FPS increase could help to manage that heavier round better. It's not proven, but the idea is out there. The downside may be that the BB flies nicely, but your target may be able to catch them in mid air though.

As has been said, "snake oil". This is not to say that wide bores have no advantage, but nothing significant has been proven. Most guns that I have seen shoot successfully with a 6.10mm shot about the same with a 6.04mm. The 6.01mm needed a bigger spring to have the same or similar FPS as well as distance and accuracy.

[Zack The Ripper]

Originally Posted by Ricochet

Wider bore are becoming popular again and seem to be having great success. Here's my issue with them and any other airsoft product. To me it's "all" about accuracy and distance, period. I want my gun to shoot as far and precise as possible, while still living within three parameters; the FPS limits of the fields I play, good quality 6mm BBs, and lastly the time it takes for my BB to arrive.

The best Airsoft barrels I have ever seen are the Prometheus 6.03mm for the Tokyo Marui VSR, and the Systema 6.04mm for their PTW, as well as variations of each. I have seen successful 6.00mm, 6.01mm, 6.02mm, but I've seen just as many or more that didn't work. The BB flight would become unstable and erratic. Theories here are that the bore is too tight and that the BB contacts the inside of the barrel too many times or it's disruptive to the hop-up spin, etc. But 6.04mm and 6.03mm are solid with great results. Most airsoft guns up until a few years back came stock with 6.08mm barrels, and even though some still do, many have gravitated towards the 6.04mm.

A gun is only as good as the sum of it's parts. Barrel, hop-up, nozzle, piston, gears, motor, etc. They all combine into what your gun is capable of. Precision pieces are not always enough, they must work with each other in harmony, as well as fit tighter properly. That is why certain systems have had great success. PTW is a good example. Every piece is machined perfectly and just clicks together. There's no play, no wiggle, and everything is high quality. We've all seen, or at least most of us, their superiority in action. If you were to lessen quality, lessen precision, etc, you will have negative effects on performance and longevity of the gun. So no matter how much you upgrade those parts, without all of those tolerances you won't have the same effect. Your gun has a maximum output level and although you can modify little things here and there, it'll never push past this performance.

Next and most forgotten is FPS limits. People conveniently forget this one when talking about distance and performance. "I one time saw a gun shoot this (--) far!" Is the equivalent of "my friend once caught a fish this (--) big". If you have the best, or one of the best guns that perform on a field, is there one out there performs significantly better? Sure there is, somewhere, but let's be frank. What were doing is projecting a 6mm BB down range, period. The physics here are what they are. I once saw a gun shoot a disgusting amount of distance, but its FPS was also ridiculously high for that time. Something like 750 FPS plus. It wasn't allowed to be fielded, and I can't recall it being especially accurate, but that BB sailed out of the barrel with zest, you bet you boots it did. Higher FPS only gives us one advantage, and that is you can use a heavier weight round, which are proven to have more stability for longer range. My 300 FPS pistol will not successfully launch a 0.30g round down range, just not enough power. I could try a more aggressive hop-up to help manage the weight, but really it needs a bigger push overall. Not to mention that too heavy of a BB travels excessively slow and if too slow can destabilize mid flight quite easily. There goes your accuracy, or your target just Matrix'd your BBs. So you want to use the heaviest weight BB your gun can shoot stable, that also doesn't arrive next week. So bumping up your FPS a bit can get you to that next weight, 0.28g, 0.30g, 0.32g, 0.36g, etc. You will likely "need" a very aggressive hop-up at this point though, and you're still stuck at your fields FPS limits, such as 400 FPS, etc. So if 400 FPS is the maximum, then you are stuck within that set of physical limitations, and that's that.

So onto wide-bore barrels. We've established the basic properties of quality parts, BB weights, Velocity, etc, and now your gun is already to go. So here's my three issues with going wide bore. Firstly you have to bump up your FPS to compensate. Due to the width of the inner bore either your air cushion doesn't have the same effect or it's able to escape forward past the BB at a greater rate. So you have to up your FPS to push the same BBs down the tube. This puts more stress over all on your gun because you'll need a bigger spring. What you can do with an M110 spring and a 6.04mm barrel, you'll need a M130 to do with a 6.10mm barrel. Secondly I'm not seeing difference in overall performance. I have seen some wide bores work wonderfully in some platforms, but not really out shooting or more accurately shooting than tighter bores with other combinations, necessarily. Third is that like most other barrel technology, we just don't know for sure.

Airsofters have been monkeying around with the physics of guns forever. Don't get me wrong, this is how things improve, but many times we change something with little to no effect, and then the fad dies out. My theory is this; if a barrel has the ability to hold a stable air cushion and is of high quality, it shouldn't matter which bore you use. Just like tighter bore increase your FPS, wider bore decreases it. So we've seen really tight bore barrels cause destabilization, not always, but it does happen. We're using 6mm BBs that actually, and usually will measure more closely to 5.70 - 5.90 if you want to get out the micrometer and measure thousands of them. This means if your barrel is too tight, then it's just too tight. Low quality BBs have actually been known to fluctuate in size more wildly and even be too big. You can see the issues with using 6.00mm BB in a 6.00mm barrel then. Also it may scrape, run, bounce, or contact the barrel all the way out causing destabilization in flight. There have been some successful cases of 6.01mm or other tight bore barrels being used, but usually in shorter barrels. Perhaps the short length helps stop the BB from bobbing around before it leaves the gun. Who knows? What I can tell you is that at a certain bore, it doesn't seem to matter. For instance at 6.04mm a short or long barrel can be used in any platform with success. Of course that's as long as the right parts, hop-up, and BBs are used. So realistically once you find a stable bore size such as 6.04mm, why go bigger? As long as the you have a stable air cushion, the right hop-up and rounds, what's the difference? I'll tell you again. The wider you go, the more FPS you need for compensation, meaning a bigger spring or more gas, just to get your gun to where it'll meet field limits and handle heavier rounds. At the end of the day a 6.04mm shooting a 0.25g round, with a M110 spring is about the same performance as 6.10mm shooting a 0.25g round, with an M130 spring. All we've done is increased pressure on our whole system to run that tighter bore.

Like I said, it all comes down to how far and straight your gun shoots, period. If you don't get an increase in overall range and accuracy, the. You've accomplished nothing. And in order for some technology to be considered legit it had to work better across the board. I have seen some airsoft guns beat up, broken, duct taped together, with low grade crappy parts in them shoot just fine. But for every one of those, there's a million that fail.

So what are the possible benefits of a wide bore? Well "in theory" you could run longer barrels more successfully because you lessened the chance of barrel fouling. More room could mean a smoother transition. Another is BB weight could make a difference. Having issues getting that 0.32g BB to fly nicely out of your gun? A wider bore, with a good hop-up, and the appropriate FPS increase could help to manage that heavier round better. It's not proven, but the idea is out there. The downside may be that the BB flies nicely, but your target may be able to catch them in mid air though.

As has been said, "snake oil". This is not to say that wide bores have no advantage, but nothing significant has been proven. Most guns that I have seen shoot successfully with a 6.10mm shot about the same with a 6.04mm. The 6.01mm needed a bigger spring to have the same or similar FPS as well as distance and accuracy.

Word to your mother.

[Styrak]

They work on fairy dust and unicorn farts.

Trust me, I'm a gun tech.

[T-Hell]

Human lube. I tell you.

Awesome write up frank.

[Red Dot]

I don't want to clutter this thread but I wonder how the Prometheus Delta Strike barrels factor into Frank's equation(s).

It's 6.20mm bore (seems negative for stock AEGs) and made of brass(?) inferior to SS. However it has 3 contact points for the BB including the bucking (a positive) and the wider bore isn't as prone to fouling (another plus). Thoughts?

[ThunderCactus]

brass is not so much "inferior" so much as it scratches a bit easier and is significantly more susceptible to CORROSION
In terms of immediate performance, brass has not proven to be inferior

The contact points are just one more way to try to position the BB to get the hop rubber directly over head, and impart a perfectly vertical backspin on it.
I can't say for sure since I haven't tried one, BUT, I figure you won't see much improvement over a conventional setup.
Fact is, if a hop rubber is off center, it's going to be off center whether the BB is perfectly centered in the barrel or not. And the BB is going to become perfectly centered by the backspin and air pressure forcing it down the barrel.
That being said, I'd really like to see one work. There's no substitute for field testing!

Sorry Rusty, wasn't trying to start something, but this is a thread about proven points. If you've got a reason for something, back it up with your conclusions! I thought you were making a "my fish was this big" statement lol
However, the swing of the market doesn't help your findings. If the twist barrel was really an improvement, I've reason to believe more companies would have jumped on board by now.
What fps are you using that twist barrel at?

[Ricochet]

Yes, this definately feels sticky. I don't know if I'm talking about this thread or ThunderCactus in general.

I wanted to add something. It has been proven that FPS does not provide the advantage as once thought. Solid hop-up, good BBs and a good barrel are your primary tools for success. BUT, there are two advantages to higher FPS that must be mentioned for contrast. Firstly, no matter how good the spin from your hop-up, it'll still take sufficient velocity to even get certain weights of BBs to fly, or fly for a reasonable distance. The heavier the round you use, the more potential you have for stable flight over long distances. So keep that in mind before thinking an R-hop will be enough, especially outdoors. Secondly, is how quickly the round arrives on target. There are two advantages here. For starters the target is less likely to dodge the shot, but also the faster the BB gets to where it needs to be, the less time the spin has to degrade. So you still want appropriate FPS in the equation for balance.

[ThunderCactus]

To add on that;
It IS a balance of fps and weight.
FPS alone won't give you any real improvement.
If your hop rubber can't lift anything heavier than a .25, then obviously you won't gain any extra range with heavier ammo.
If an Rhop on a stock marui can lift .30s, you better believe it will actually increase your range. It's also why some of us run heavy ammo in pistols.

Your idea of lighter BBs getting to their target faster is both correct and incorrect.
If the lighter BB is traveling say 25fps faster than the heavier BB, there is a point where a lighter BB will lose so much velocity in flight, that a heavier BB will actually arrive on target BEFORE the lighter BB. This would be comparing two guns both at 400fps, one using .28s and one using .30s.
If both BB's are fired at the same relative velocity, the heavier BB will arrive on target first since it doesn't lose as much velocity in flight. This would be comparing a 380fps gun on .28s versus a 420fps gun on .32s.
In shorter distances, of course a lighter BB will arrive first, that's why they're the best choice for CQB.
So depending what ranges you're engaging at.... in CQB at 25-100ft, a .25 would most definitely be advantageous over a .30

If the hop spin destabilizes before the end of the flight path, that's a clear indicator that you need to use heavier ammo.
The inherent problem with lighter ammo is it tends to naturally have defects. Like .20s and .25s tend to have bubbles, or just tend to be less accurate. Whether you shoot a .25g BB at 280fps or 500fps, the accuracy will be about the same. It's going to destabilize just as fast at 280fps as it does at 500fps, it's just more noticeable at 500fps since the round won't be dropping short all the time.
What I've been finding over the years is that there's a sweet spot of velocity that every 6mm spheroid likes to be at, and that's a relative velocity of right around 330-340fps. At 380fps we recommend .28s, and at 420fps we recommend .32s, the relative velocity remains constant at ~330fps, but the range increases since the .32 loses it's energy less quickly.
That could be incorrect since I don't have free access to some nice heavy rounds .36-.43, but so far that's what I've found.

It somewhat comes down to personal preference. I don't notice too many people trying to dodge my BBs, so I run as heavy ammo as possible to increase my range and accuracy. I'd rather have a chance of hitting someone at 300ft and deal with them dodging them if they see it.

[ThunderCactus]

Made some revisions and spelling corrections

[The Legacy]

Hi, thanks again for posting this, and linking it when I had posted about making my M14 DMR about a year ago.

I wanted to ask a few quick questions, as I'm about ready to make the necessary purchases:

1) Which is better, a Prometheus or a PDI?

2) Where is the best place to buy the parts for an M14? I know of http://www.airsoftparts.ca, but I don't know if they have the parts I need.

3) What is a 'Ported Cylinder'? Is that the small hole in the side of a cylinder? If so, I found this video does a great demonstration of how it affects FPS. Regarding this, for an M14 long barrel, what would be the best kind of ported cylinder for that kind of situation?

4) And finally, the biggest question of all: Should I use a short inner barrel in a long barreled M14, or a inner barrel that's the proper length to match the outer barrel? What are the side effects of using a short inner barrel for a long-barreled gun?

Thanks again! I felt that these questions would be useful for this post, not to mention the bump for others.

[Hectic]

1) prommy, but not by much. These days even madbull makes a nice barrel. Lol
2)you alrdy found the best place, however a google search will net a million places that sell parts
3)correct, the port is the hole. The type you want will depend on barrel length, velocity and bb weight. Example a 400fps build (m110-120) long barrel say 455mm youll want a full cyl (no port) and some .30g bb's
4) i would say fill the length with the inner. Why? Because i have had guns that the bb would hit the outter if the inner was too short. I should add that a much longer barrel wont make much difference in performance. I had an mp5k (pistol length barrel 110mm i think) with a bridge hop shooting 380ish that could range with my 510 and 455 and 363mm inner barreled guns. Just match the air volume well, making sure to go over a little bit (i find the full cyl, 455inner @380-410fps on .20's to be ideal for running .30 bbs, with either a flat or bridge hop)
I will add tho that you dont have to fit the inner to the outer just i have had issues with it so i try to avoid it, keep in mind alot of stock m16 length guns come with m4 lenght barrels and run without issue (this is so the companies only have to build 1 kind of gearbox for the AR line of guns,;mainly cyma, jg, china guns )

[ThunderCactus]

Every cylinder comes with a length range, stick to the lower range
with a 300mm barrel you want a cylinder for 300-380mm
reason being it makes the gun more energy efficient on heavier ammo.

And personally i wouldnt go longer than 14.5" or 363mm. As i said, the longer the barrel is, the faster it will foul. And the 14.5 is going to be just as accurate as a 455 or whatever. best to use a socom m14 with the short barrel.

As far as a short barrel in a long outer, it really shouldnt matter. Systema has always used 14.5" barrels in their 20" M16s.
it only takes about 2ms or less for the bb to get from the end of the barrel to the flash hider, and if you dont have at least a 6mm grouping at 12", you have some serious issues with your gun lol

[J-Man19]

I'm sure this has come up multiple times already, but I can't seem to find any threads.
If we take away the obvious factor of cost, why couldn't rifling work on a bullet shaped bb? Delete hop up all together.

Looking for the science behind why it isn't done, not the cost.

[Danke]

Originally Posted by J-Man19

I'm sure this has come up multiple times already, but I can't seem to find any threads.
If we take away the obvious factor of cost, why couldn't rifling work on a bullet shaped bb? Delete hop up all together.

Looking for the science behind why it isn't done, not the cost.

It would work fine but you wouldn't want to be shot by it.