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BB weight and range: WHAT is the truth?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: POLAND_SPUD » Sat Oct 10, 2009 9:35 am

try chairgun

that's a pretty good programme for airgun ballistics...
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Unread postAuthor: Ragnarok » Sat Oct 10, 2009 9:37 am

lozz08 wrote:Not the effective range for different pellet weights at the same energy level...

Which is a question which you can't really answer until you define "effective range" in a mathematical sense. What trajectory drop, velocity or time to target defines a pellet as having become "ineffective"?

The computer doesn't know what "effective range" is. You need to tell it.

When you have an answer to that, then you can tell a computer to work out effective range.
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Unread postAuthor: Davidvaini » Sat Oct 10, 2009 10:43 am

and effective range is not only determined by the velocity and weight of the projectile, but also the quality of the hopup. Remember, for range hopup is the most important thing for an airsoft gun since they shoot spherical projectiles.

Figuring out how much backspin a certain hopup produces is near impossible to figure out, and even if you did, you want an adjustable hopup because sometimes you need to adjust your amount of backspin(especially for sniping situations).

Its also important to note there is a huge difference between range and effective range. I can aim my p90 at a 45 degree angle and get 300+ foot shots, but it doesn't mean I can hit a man size target easily by doing that. Measuring effective range would also have to account for barrel accuracy, windage, how dirty your barrel is, and a number of other factors.

High quality machined airsoft guns don't even have what you would call "very good consistent accuracy(4 MOA or lower)

Really a BB weight,BB Velocity,Range, Effective Range, Accuracy chart, even if it could be done, would have to be an independent chart for the individual gun.
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Unread postAuthor: jimmy101 » Sat Oct 10, 2009 12:20 pm

Davidvaini wrote:and effective range is not only determined by the velocity and weight of the projectile, but also the quality of the hopup. Remember, for range hopup is the most important thing for an airsoft gun since they shoot spherical projectiles.

Figuring out how much backspin a certain hopup produces is near impossible to figure out, and even if you did, you want an adjustable hopup because sometimes you need to adjust your amount of backspin(especially for sniping situations).

Isn't the "effective range" (defined by a particular level of reproducibility) increased with a hopup regardless of if the hopup gives the spin needed to provide lift?

Effective range is not just distance, it also includes reproducibility. A "hop-up" increases reproducibility (for a spherical ammo from a smooth barrel) but only increases range if it is oriented properly. It's possible to increase "effective range" even though the maximum range might decrease.

For example, a paintball gun with an effective hopup might have increased effective range even when it is fired upside down so that the round is spinning the wrong way and dropping faster than it normally would. The hopup makes the gun more reproducible (for a given firing aspect), which may be a larger affect than in increase or decrease in maximum range.
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Unread postAuthor: lozz08 » Sat Oct 10, 2009 7:19 pm

Alright, forget the hopup then, I'm just trying to find out what around about where the "sweet spot" would be in terms of bb weight for a given energy level. Like I'd like to make a graph of muzzle energy vs. best bb weight.
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Unread postAuthor: Ragnarok » Sat Oct 10, 2009 7:43 pm

lozz08 wrote:I'd like to make a graph of muzzle energy vs. best bb weight.

Again, you need to define "effective range". Until you've decided what conditions define a BB as ineffective, you cannot possibly create such a graph (at least, one that would mean anything valuable).
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Unread postAuthor: lozz08 » Sat Oct 10, 2009 9:42 pm

Hmm, I see what you're saying now... I guess different things are acceptable to different people... There are a lot of variables here. For me, an acceptable meaning of "effective range" Would be the range at which the bb drops by one meter, as beyond that you're really aiming a bit low on your scope.
Obviously more problems come when you start thinking about the hopup lifting it above the original launch altitude, then who knows wtf is going on. But I think it is true that my hopup is most important. The problem is setting it up so that the spin is as close as possible to perfectly backward, and not on an angle so it sprays off to the side.

But I would like to test all the bb weights with no hopup, at a 0 degree angle to the ground, given the same energy, to see which land further.


Chairgun is really good, btw, thanks for that. It's great to see the effect of zeroing your scope further out, how that effects your range. I suppose it doesn't take into account hopup. Does anyone have any idea at all how much higher the bb elevates with say a moderate hopup? I know it will depend on weight, but lets say 0.25g here. Im just wondering like what sort of range we're talking here, 0-0.5M? 0.5-1.5M elevation?
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Unread postAuthor: Davidvaini » Sun Oct 11, 2009 12:00 am

jimmy101 wrote:
Effective range is not just distance, it also includes reproducibility. A "hop-up" increases reproducibility (for a spherical ammo from a smooth barrel) but only increases range if it is oriented properly. It's possible to increase "effective range" even though the maximum range might decrease.

For example, a paintball gun with an effective hopup might have increased effective range even when it is fired upside down so that the round is spinning the wrong way and dropping faster than it normally would. The hopup makes the gun more reproducible (for a given firing aspect), which may be a larger affect than in increase or decrease in maximum range.


that is why I proceeded to mention about accuracy with MOA ratings.. and how effective range is also about accuracy.

Effective range is, "optimized range where you can hit the target constantly with good accuracy." How much you adjust your hopup a long with your BB weight, consistency of velocity, weight of the BB, quality of your barrel and a few other things factor into this.
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Unread postAuthor: Tsukiten » Sun Oct 11, 2009 5:34 am

inonickname wrote:Within reason, usually. You can't fire a neutron star and expect it to go far.

It would fire you, lol

BTW
Hop-up on heavy bb --> less influence --> minus kenetic energy loss (less)
Hop-up on light bb --> more influence --> minus kenetic energy loss (more)
thus, ---> comparable range

:o ?
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Unread postAuthor: POLAND_SPUD » Sun Oct 11, 2009 8:54 am

It's great to see the effect of zeroing your scope further out, how that effects your range. I suppose it doesn't take into account hopup

it designed for airgun pellets so you can't model the effect that hop-ups have... in fact I think that time of flight is the most important graph for comparing different ammo
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Unread postAuthor: psycix » Sun Oct 11, 2009 9:47 am

lozz08 wrote:steel bbs that probably weigh like .5g.

I've got 6mm steel bb's. They weigh 0.89 g each.

They do respectable damage when firing at 8 bar. Currently I'm working on something fully auto that does it at 19 bar... :D
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Unread postAuthor: Ragnarok » Sun Oct 11, 2009 5:05 pm

lozz08 wrote:I suppose it doesn't take into account hopup.

It doesn't, and there's no (accurate) way to estimate lift using a program that's not built for it.

~~~~~

Taking the most effective BB to be the one that has least time to target, I've gone off and done some calculation, and the results tell me that I've been an idiot.

Ignoring changes in Cd with velocity (which Chairgun also does) initial energy is irrelevant, and I should have known that from the off. That is to say, that for a given range, there is one BB weight that will get there in less time than others, regardless of the muzzle energy involved.

So, whatever the energy of a given airsoft gun...

0.12g is least time up to 8.5 metres.
0.20g from there up to 12 metres
0.23g from there up to 13.4 metres
0.25g from there up to 14.8 metres
0.28g from there up to 18.2 metres.
0.30g from there onwards... although I didn't do anything for heavier BBs.

The important thing is that the 0.30g BBs, although the range needs to be more than 18.2 metres for them to get there in less time, up until that point, they are only ever a maximum of 16 milliseconds slower to any range up to that than ANY other BB.

I should note that at any REAL distance, because the lighter BBs lose velocity so fast, the heavier BBs retain the most velocity.
Past about 10-12 metres, the 0.30g BBs are travelling faster than anything else. (And their additional velocity retention will mean they'll keep more lift further from the muzzle, as lift is dependent on airspeed velocity.)

But in a similar way to the fact that the 0.30g BBs aren't ever that much longer to the target than any other BB, the inverse is somewhat true. The lighter BBs aren't ever too appalling beyond their optimum range (except 0.12g, which is a joke.)

In best terms, I think the answer is to go for the heaviest BB that your hop-up will adequately lift/stabilise, as they'll have the best "time to target" (at least, where the difference matters), will retain lift better (for a more favourable trajectory), as well as keep energy longer (meaning hits will be noticed.)

But I wouldn't recommend 0.12g for any airsoft gun, unless it really IS the only thing you can use (in which case, get a gun that actually works). It loses velocity too fast, so loses its lift quickly, and at longer range, your target may well not notice a hit.

Of course, I stress that this is a purely mathematical approach to the question - and it is using a crude ballistic model (it's easier to do this outside the LRC). It is not based on actual experience of airsoft play - but it is based on ballistics experience.

Feel free to quote this post on Airsoft forums in any such debates (or just be sneaky, and keep the information for your own advantage in your games.)
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Unread postAuthor: lozz08 » Mon Oct 12, 2009 2:00 am

Well, that's kind of the answer I've been looking for. I do find it interesting that programs like airsoft calc quote a higher effective range for lighter bb's, when it clearly just ain't true no matter how you look at it.
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Unread postAuthor: Ragnarok » Mon Oct 12, 2009 6:34 am

@lozz08: I've gone and looked at "Airsoft calc", and it makes a highly laughable mistake.

It assumes gravity to be 9.8 m/s. Not an acceleration of 9.8 m/s<sup>2</sup> - just a plain velocity of 9.8 m/s. Someone needs to teach the guy who wrote it basic physics.

I should note that it also certainly doesn't account for drag (or lift).

Put simply, I could write a better calculator than that in a half afternoon. Given the guy did the first version 4 years ago, that's appalling.

I'm almost tempted to fire up my Arnie's Airsoft account and actually go and tell the guy what mistakes he's making.
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Unread postAuthor: lozz08 » Mon Oct 12, 2009 8:30 am

Oh no... That is pretty bad isn't it? I might try and find a proper program... Know of any? I could only find calc. And I'm no good at calculating any sort of resistance due to anything, otherwise I'd calculate it myself. I guess the drag on a bb of that size has a pretty set value for a certain speed, but a speed vs. Time graph wouldn't be too easy because of the fact that air resistance decreases as speed decreases, so we'd have a few too variables for my skills.

Edit: Airsoft calc is giving me the same answer for effective range as this site: http://www.arniesairsoft.co.uk/?filnavn ... s_calc.htm
And that quotes a good formula. Maybe you are looking at an old version?
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