Airsoft Sniper Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
2,893 Posts
Discussion Starter · #1 · (Edited)
I'm making this write-up because the only way to achieve greater accuracy is by understanding why different things make our bbs more accurate, or inaccurate as the case may be. We should also understand how our sport of airsoft works because not knowing why our hobby works just isn't right.

--------------------

Why The Hopup Works:
We all know the bucking gives the bb a backspin, which keeps the bb from falling to the ground. Too many people though don't even know why this happens. The whole idea behind the hopup is the Magnus Effect. As the bb is flying through the air, the backspin creates a low pressure zone (going into aerodynamics here) on the top of the bb, and a high pressure zone on the bottom. What this does is suck the bb up into the air. We can't just give it backspin and expect it to work perfectly though, we need to get just the right amount of backspin to counter gravity. This is how we get that flat trajectory.

One way you can see an exaggerated version of the Magnus effect is with a ping-pong ball (table tennis ball) because of the high surface area and low mass. Try throwing the ping-pong straight through the air while giving it a backspin. Then try throwing it with the same strength and speed, but giving it a forward spin. You'll see the ball flies much straighter with the backspin than with the front spin.

--------------------

BB Vibration:
The bucking makes the bb have a backspin, but if that backspin is applied too fast the bb will vibrate in the air as a result of the center of rotation being off the center of mass (like drilling a hole for an axle on a wheel off center and trying to spin it). This vibration makes the bb unstable and causes inconsistencies in the flight patterns. It also makes the backspin slow down faster than it should. The slower the backspin is applied (like with an r-hop), the more stable the bb is, the more consistent it will be, and the longer it will maintain its flat trajectory.

--------------------

Momentum By FPS:
Giving the bb more momentum by increasing fps will only help if gravity is somehow turned off and the bb maintains a straight trajectory forever. Unless that happens the bb will run out of backspin and fall to the ground long before you run out of momentum. Of course you may lose enough momentum that the person may not feel the bb hitting them, but that doesn't happen very often.

--------------------

LRB (Long Range Barrel):
What the LRB does is stabilize the backspin by forcing the bb to the top of the barrel as it exits, so the bb basically rides along the top. This stabilized backspin then allows the bb to maintain it's straight trajectory for a longer period of time. You want to get as straight a trajectory as possible.

One thing to note is that an LRB doesn't give a perfectly flat trajectory - it's a very wide parabola that opens up. The bb is actually climbing for most of its flight until the last little flick at the end, when it starts to fall. That's why the LRB is so desirable - its path is even more predictable than a flat trajectory because an arc is more physically stable than a line.
--------------------

Why The Size Of The Bore Matters (Barrel ID):

Less contact with the bb means you have fewer external forces interrupting the flight and rotation. Therefore, wider bore is better. Too wide gets you turbulence, hence my dislike for the ORGA barrels. The sweet spot seems to be 6.03-6.05, but the quality of the bore is always top priority, and Prommy 6.03 has the nicest bore, in my experience.

(Credit goes to Cheese Man for writing this)

--------------------

I'm sure I'm missing something, or I got something wrong, so please if something can be corrected or made better, as always just tell me. It will make this write up better and help me and anyone who reads it.
 

·
Registered
Joined
·
953 Posts
Could it be argued that an LRB with a 6.01 barrel could have a greater stability than a larger bore, as the tighter bore would conform to the BB better? Or would that only work in a perfect system, where no vibration is present? Because couldn't that throw the BB around even more if it's tighter?
 

·
Registered
Joined
·
49 Posts
This post was very helpful, Thank you. I had a general concept on how the hop up worked, but nothing exact. I see why it's so important to get your hopup just right, now.

Very informative.
Very helpful.
 

·
Premium Member
Joined
·
2,311 Posts
Any outside forces on the bb will impact the spin. That is why you want a wider bore. The bb's spin acts like a gyroscope and it keeps the bb from wobbling in midair *if the spin is applied gradually and properly*

Just remember, slow is smooth, smooth is fast. That applies to just about everything with an airsoft rifle. Hell, i just finished a piston mod that doesn't release the nozzle until it hits a certain pressure (I read about it on another forum and thought I'd try it) and now I can have my piston moving at less than .02 m/s.
 

·
Registered
Joined
·
2,893 Posts
Discussion Starter · #7 ·
Cheese, can you elaborate on why a wider bore is better? If you do I can add it to the original post. And can you link to the mod you're talking out? That sounds really interesting.
 

·
Premium Member
Joined
·
2,311 Posts
Less contact with the bb means you have fewer external forces interrupting the flight and rotation. Therefore, wider bore is better. Too wide gets you turbulence, hence my dislike for the ORGA barrels. The sweet spot seems to be 6.03-6.05, but the quality of the bore is always top priority, and Prommy 6.03 has the nicest bore.

The mod I'm talking about never had a formal guide as far as I know, I just saw that somebody did that (never knew how) and I just tried it. It's not difficult, I'll write something up when I get it perfected.
 

·
Premium Member
Joined
·
2,311 Posts
Add "in my experience" to the end, there are people who will disagree. Thanks. :)

One thing to note is that an LRB doesn't give a perfectly flat trajectory - it's a very wide parabola that opens up. The bb is actually climbing for most of its flight until the last little flick at the end, when it starts to fall. That's why the LRB is so desirable - its path is even more predictable than a flat trajectory because an arc is more physically stable than a line.
 

·
Registered
Joined
·
2,893 Posts
Discussion Starter · #11 ·
I added the "in my experience" part. Can I quote you on what you just said about the LRB?
 

·
Registered
Joined
·
2,893 Posts
Discussion Starter · #13 ·
I'll do it a little bit later, thanks. For some reasson I can't make new paragraphs with a boxee box (google it).
 

·
Registered
Joined
·
838 Posts
I wonder the diameter size of bb is important or not ? I see common BB Brand ~ 5.95 +/- 0.01mm, some other 5.98 +/- 0.01mm. :D
 

·
Registered
Joined
·
2,893 Posts
Discussion Starter · #15 ·
I just added the quote about the LRB not having a perfectly flat trajectory.
 

·
Premium Member
Joined
·
1,048 Posts
I wonder the diameter size of bb is important or not ? I see common BB Brand ~ 5.95 +/- 0.01mm, some other 5.98 +/- 0.01mm. :D
The importance of the diameter is purely dependent on your bore size. If you are using a tightbore, it is better to use a 5.95 because it minimizes the chance of contact with the barrel and the chance of jams. If you use larger barrel bores like 6.07 and such, you can be closer to the 6mm "standard" for bb sizes as this will not have as large of a chance to have any negative effects on the bb.
 

·
Registered
Joined
·
5,239 Posts
I dissagree how you think that the FPS does not give you range. (I can't be bothered arguing about it though so I will just give you a link that answers it)
Check out the velocity comparrisons on this study on bb dynamics.
ATP - The Airsoft Trajectory Project
This shows that FPS does effect distance and the higher the FPS the more range.

I have played for many years and I believe that this is a false myth that people in the airsoft world have started to beileve.
 

·
Registered
Joined
·
564 Posts
Yeah so does that mean if you get 0ft at 1fps, and you get 250ft at 400fps, wouldn't that prove that the higher the velocity = the further the range? Or is there a certain fps that platforms, and regardless of how high the fps is, the range stays the same?
 

·
Registered
Joined
·
838 Posts
Seem it pretty old information from that link, not sure it still correct. If you said more FPS , more effective range. Then why pretty much gunw have high FPS out of box don't got effect range like the chart. Then I can updrage spring and got more range and effect range, right ?

I think keep FPS in some certain range ( 300-500 example ) will give best effect range can have
 
1 - 20 of 30 Posts
Top