.25g BBs have less energy than .20s

[Hedganian]

A heavier BB will accelerate slower in the barrel, due to its greater inertia, thus it will remain in the barrel for a longer time, enabling it to accelerate for longer and absorb more energy than a lighter BB which exits the barrel sooner. The heavier BB retains its energy for longer in flight, again due to its greater inertia, and thus can fly farther and may have a higher velocity at a given range.

 

It's simple physics. Perhaps not that simple, as I'm seeing some really shaky physics in this thread.

 

I suggest reading this article on the subject of 0.2g BBs vs 0.25g BBs: FPS, Distance and Time

[transist]

.25 is better in every way except for raw velocity. More energy, more range, more accuracy, etc.

 

VARIABLE's charts are pinned in this forum. Take a look at those as well.

[w733commando]

I still can't see why a 0.25 would have more energy upon exiting the barrel than a 0.2. The mass difference is accounted for by a velocity difference, and I can imagine that there would be a consistent value of energy. The energy of the BB is determined by the spring, and the spring doesn't produce less energy when propelling a heavier BB. However, if the readings were taken 10 ft away from the barrel, then the heavier BB would have retained more energy than the lighter BB, despite the initial energy being the same.

[crunkathon2k]

I still can't see why a 0.25 would have more energy upon exiting the barrel than a 0.2. The mass difference is accounted for by a velocity difference, and I can imagine that there would be a consistent value of energy. The energy of the BB is determined by the spring, and the spring doesn't produce less energy when propelling a heavier BB. However, if the readings were taken 10 ft away from the barrel, then the heavier BB would have retained more energy than the lighter BB, despite the initial energy being the same.

 

 

Quoted for truth

 

I would like to see more math, the formula for kinetic energy is 1/2 m v^2

 

My math still seems legit to me, I'm taking a equal to or less than approach for the INITIAL energy of .25 g.

 

The initial motivation for me making this thread is I have been having trouble penetrating a coke can with 320 fps guns with .25s, when it is easier to do with .20s

[Azulsky]

All weight bb's have the same energy as they leave the muzzle. This has nothing to do with fancy math. If the same spring is behind the piston pushing the bb's the force is the same.

 

The difference in energy with different bb weights varies after the muzzle as lighter bb's are more affected by external forces, and therefore have lower energies at the same given range as a heavier bb.

 

For instance

With a 2 Joule Spring any bb leaving the barrel will have 2 joules of energy as it leaves the barrel. At 50 feet the .20 gram bb might have 1 joule of energy while the .25 might have 1.25J of energy.

 

 

Think about it like this:

you are inferring that the laws of physics are inaccurate based on a coke can.

[Sale]

Air resistance affects the BB already inside the barrel, and inertia works both ways as Hedganian pointed out: A heavier object will accelerate more slowly, so it will spend more time in the barrel, absorbing energy produced by the spring. The spring produces a fixed amount of energy, yes, but a heavier BB uses that energy more efficiently. Also as the heavier BB moves more slowly, it faces less air resistance (inside the barrel), so the spring is able to push it more easily.

 

The above is just a couple of theories and certainly not exhaustive, but the theory is solid fact in principle, and the results can be easily observed in practice. It's been done several times by various independent testers, and virtually every time using heavier BBs made the muzzle energy creep a bit higher. In the odd case where this didn't happen, it was at least equal. Never lower.

 

-----

 

Even if the energy was the same, the momentum of a 0.25g BB is higher. Momentum is P=mv. Let's look at these two BBs, both leaving the muzzle with an energy of 1.13 joules (350 fps with 0.2g and 311.86 fps with 0.25g).

 

0.2g * 350 = 70 g/s

0.25g * 311.86 = 77.965 g/s

 

Of course as the heavier BB carries more energy in practice, the difference in momentum will be even bigger than this.

 

True .25 will have a lower velocity but its been proved that actually .25s carry more energy than .2 in all cases, which would explain why systema apparantly test their springs with .25 bbs and TM package guns with .25 bbs.

Systema uses 0.2g as the control BB and that's how their springs are rated. Says so on the back of the spring package. The one exception I remember from years back is when the M120S (as opposed to M120 OT) was too strong. That may have started rumours about Systema labeling springs according to m/s with 0.2 gram BBs.

 

-Sale

[Azulsky]

Do you have test results that demonstrate the first theory with AEG's. I have only thought that to be true(at least to a practical extent) with gas rifles as the propulsion is an actively expanding gas instead of an AEG which more or less only pushes a gas. For curiosity's sake at least.

 

Thanks for doing the math for the OP though.

[Sale]

You are correct that the difference is very small with AEGs, while gas guns show a more pronounced "energy creep". My point was that I've never seen an AEG produce lower muzzle energy with heavier BBs. Only marginally higher or the same.

 

Stealthbomber made a test like that, my mates did that, and I've done it myself as well. Sadly I didn't record my own results to show accurate data to others, but let me see if I can dig up some data.

 

EDIT: Here's a picture from an article that compared the velocity of various BB weights downrange. It shows primarily how BBs behave after leaving the barrel, but the editor noted that heavier BBs also showed a higher initial muzzle energy.

 

 

This does not exclude the possibility that the actual weight of the BBs is different from the label, or that they may be higher quality or have a larger diameter. If you calculate the energy based on 0.25g on the package but the BB actually weighs 0.24 grams, the BB will appear to have a higher energy than it does. For accurate results, BBs should be weighed and measured in addition to chronoing them.

 

Still though, there's nothing that debunks the explanation why heavier BBs produce higher velocity: Less velocity means less resistance. Less resistance means more energy.

[expvideo]

In real life, the m16 has a smaller bullet and about the same powder as the 7.62 x 39 mm round used by the AK. Thus, it has a much higher initial muzzle energy because it shoots at such a high velocity, much like the .20 g bb. The AK shoots at a lower initial muzzle velocity, but, like the .25 g bbs, has a more stable flight path from its weight.

:rofl:

 

 

7.62x39 has much higher muzzle energy than 5.56. Of course we aren't going to discuss that here, but check this link:

 

http://www.on-targetrange.com/energy.shtml

[crunkathon2k]

It appears I have made a fool of myself in this thread

 

I did do the math correctly, but I probably assumed too wide of an FPS margin. The laws of physics do not lie (in most cases where classical models of force and motion apply), so my kinetic energy calculations do make sense assuming the inputed information is also correct which, in this case, is too much of a wash to reach conclusive statements.

 

I now change my view to Sale's view that .25s should be equal or greater than, not equal to or less than.

 

And sorry about the 7.62 vs 5.56 screwup, I need to get my facts straight!

[Stealthbomber]

At impact to propel the bb - more loss on the .25g as it loses velocity to propel the heavier weight against a .20g bb.

Just. No. You ave completely the wrong end of the stick.

 

I still can't see why a 0.25 would have more energy upon exiting the barrel than a 0.2. The mass difference is accounted for by a velocity difference, and I can imagine that there would be a consistent value of energy.

 

Theoretically, the energy imparted to a projectile by a pneumatic system (spring OR gas powered) will ALWAYS be the same. The gun fires the same slug of air up behind the BB regardless of BB weight.

 

In practice, however, it can be seen that the muzzle velocity of heavier BBs is actually HIGHER than calculations would lead you to expect.

A gun shooting with muzzle energy of 1.3J with 0.2g BBs will often shoot at around 1.5J with 0.28g BBs. The 0.28s WILL be firing at a lower velocity but not as low as calculation would lead you to expect.

This is the phenomenon known as "velocity creep".

 

 

My math still seems legit to me, I'm taking a equal to or less than approach for the INITIAL energy of .25 g.

Your maths is way wrong.

For a start, heavier BBs fly at a lower speed proportional to their weight and FPS. A sweeping "they fly at 50fps lower" assumption is the root cause of all your other mistakes.

 

The initial motivation for me making this thread is I have been having trouble penetrating a coke can with 320 fps guns with .25s, when it is easier to do with .20s

So, did it occur to you that your .25s might be a different diameter to your 0.2s?

[amateurstuntman]

Most of the people posting on here are just guessing.

They are also basing their guesses on faulty base principals.

A GCSE in science does not make you Stephen Hawking.

 

Those that are not guessing (you know who you are) have got it correct.

 

The closed pneumatic system in an AEG or a gas gun has a fixed amount of energy available to impart to a projectile, however a .2 bb doesn't use that available energy with 100% efficiency, a .25 bb uses the available energy more efficiently and a .28 is even more efficient.

(that is in my experience and in some guns and systems the weight of bb that achieves the highest efficiency will vary)

 

It is a combination of factors that lead to the muzzle velocity, spring rate doesn't matter (when comparing one weight to another) but barrel length, barrel bore, friction caused by the internal surface of the barrel and bb size (relative to each other).

 

For example, the heavier bb will accelerate slower in the barrel and pick energy up for longer but only if the barrel length allows it.

 

At the point that the bb leaves the barrel the gun has no more influence on the bb

 

It has a mass, a velocity and a certain amount of back spin.

 

 

A faster bb slows down more quickly because the air resistance of an object increases as the square of the speed.

For example a bb that weighs .2 moving at 115 m/s will be presented with 13225 resistances (not a real unit, just for illustrative purposes) the .25 bb moving at 100 m/s will be presented with 10000 resistances. 32% more resistance for only 15% more speed.

 

The bigger the difference between the two masses the bigger the resistance difference.

 

A .25 will lose its energy slower because it is slower.

The fact that it leaves the barrel with a bit more energy is a bonus.

 

The fact remains that I have been 'softing for many years and I use .25s in my electric guns and .28s in most of my gas guns, some have fixed hops or LRBs and I have to use the weight of bb that works best with them.

 

The reason for that is not maths, it is that they just work better.

[zentaurus]

just something to think about:

 

a) same spring, same cylinder, same piston, same gears, same batt, same hop pressure level.

 

will a .25 leave the nub point at the same pressure level (not velocity but air pressure) as a .2 bb?

 

c) and, as some has pointed out, will the .25 accelerate faster or slower?

 

d) and therefore gain/lose more energy?

 

e) and will be accelerating/decelerating as it moves away from the barrel?

 

f) and will be more efficient (conserve energy better?) as it goes through air outside the barrel?

 

as amateurstuntman sed, it's a combination (complex?) of factors and principles -- it's a system

[Scatman]

This makes me laugh, its liek peopel rying to prove gravity does't exist (jk) seriously ask youself if this is true for assuming only .25's then why do all the heavier bb's .29's .36's .43's get used by the seriously long range shooters, the pellets need to keep energy to travel over distance (correct?) so assuming that a sniper rifle shooting at 400fps using .29's will out range an aeg at 400fps using .2's, the only explanation if everything is equal bar thepellet weight is that one pellet has a greater amount of kinetic energy, correct me if I'm wrong I don't do a-level physics, the closest thing to science I do now is psychology, perhaps the dudes findings coudl be explained by an innate fear of the number .25 caused by the oedipus conflict, where hementally blocks out all examples of the number .25 being superior (only kidding)

[Scatman]

This makes me laugh, its liek peopel rying to prove gravity does't exist (jk) seriously ask youself if this is true for assuming only .25's then why do all the heavier bb's .29's .36's .43's get used by the seriously long range shooters, the pellets need to keep energy to travel over distance (correct?) so assuming that a sniper rifle shooting at 400fps using .29's will out range an aeg at 400fps using .2's, the only explanation if everything is equal bar thepellet weight is that one pellet has a greater amount of kinetic energy, correct me if I'm wrong I don't do a-level physics, the closest thing to science I do now is psychology, perhaps the dudes findings coudl be explained by an innate fear of the number .25 caused by the oedipus conflict, where he mentally blocks out all examples of the number .25 being superior (only kidding)

[w733commando]

a) same spring, same cylinder, same piston, same gears, same batt, same hop pressure level.

 

will a .25 leave the nub point at the same pressure level (not velocity but air pressure) as a .2 bb?

 

c) and, as some has pointed out, will the .25 accelerate faster or slower?

 

d) and therefore gain/lose more energy?

 

e) and will be accelerating/decelerating as it moves away from the barrel?

 

f) and will be more efficient (conserve energy better?) as it goes through air outside the barrel?

 

b.) Should do

c.) It would accelerate slower due it's weight.

d.) and therefore make use of more of the energy than a 0.2, due to its increased time in the barrel

e.) as far as I know all BBs de-accelerate as they move away from the barrel

f.) a 0.25 will encounter less air-resistance due to it's lower velocity, and also retain it's energy better than a 0.2 due to increased momentum.

 

Have I got it all right?

 

Edit:

so assuming that a sniper rifle shooting at 400fps using .29's will out range an aeg at 400fps using .2's, the only explanation if everything is equal bar thepellet weight is that one pellet has a greater amount of kinetic energy, correct me if I'm wrong

 

You've got it a bit wrong, the 0.29 would have slighter more energy than a 0.2 (due to reasons already explain in this thread), but not enough to make a lot of difference to range. The reason a 0.29 would fly further on a 400 fps gun is because it would encounter less air resistance and have more momentum. As I mentioned before, try throwing a ping pong ball and a golf ball and see which one you can throw furthest.

[PenGun]

However, what I'm trying to prove is that .25s have less initial muzzle energy. It's pretty small, but if the fps differential is about 50 fps, then it's definitely there.

 

Not this whole thing again

 

No duh...for the same imparted energy (or muzzle energy) a heavy projectile will have a lower initial velocity when launched than a lighter projectile.

This is how high velocity sabot rounds work in regular tank cannons etc.

 

A little knowledge of physics seems to be a dangerous thing in internet forums

[demon.b]

A little knowledge of physics seems to be a dangerous thing in internet forums

The internet exists to pass on and sustain (mis)information.

 

[amateurstuntman]

Here's a question for you then.

 

I have a tuned up gun that shoots about 300 with a .2 and about 35 to 40 rps depending on the battery I'm using.

 

When I shoot a single shot, I get (say) 290.

When I shoot repeated single shots at a fast rate (as fast as I can pull the trigger) I get an average of 290.

When I stick it on auto and fire through the chrono I get an average of 300.

 

Is there a negative pressure in the barrel from the passage of the previous bb that is sucking the next one out of the barrel?

Is there a negative pressure but caused instead by the rearward action of my piston that lingers long enough to effect the speed of the subsequent bb in the barrel?

Are the bbs in the air on the way to the chrono traveling through each other's turbulence and not experiencing any drag?

 

Is it something else I haven't though of that has the same net effect?

 

I don't know but there it is.

 

[MDK_Marshal]

*gibberish*

 

 

You, sir, are an Imbecile.

 

go back to your fake science and leave the maths to people with some clue as to what they're doing, eh now?

 

In all seriousness, can somebody lock this trainwreck of a thread? I can hear the metaphysical representation of Science weeping in the corner. Kudos to all the intelligent people that know what they're talking about, but the idiots have overwhelmed us this time.

 

I think that a thread detailing the physics behind airsoft guns would be very much appreciated, and would be a brilliant resource, even if only to those of us who are interested in that sort of thing.

 

This thread, however, just aint it.

 

 

EDIT: Stunt. I'll have a quick crack at answering your question before I go to work.

 

If anything, I'd assume that there's a positive pressure in the barrel on auto, as there's going to be air compressed in the cylinder that is still under pressure (slightly) when the BB has left the barrel. This would likely take the path of least resistance out of the gun - through the barrel. This would, therefore, increase the pressure behind the BB, propelling it along the barrel faster.

 

I would think.

 

I really have to sit down with my old physics textbook and sort out the equations behind all this... or try to, at any rate!

[Stealthbomber]

There shouldn't be a negaive pressure due to the passage of the BB.

A gun firing at 100m/sec and with a ROF of 30rps will see the first BB at least 10ft downrange before the 2nd BB is fired.

 

I'm no expert on air micro-currents but there's definitely no way the first BB has a direct effect on the 2nd one.

 

I've noticed this as well and, TBH, I just put it down to increased mechanical efficiency due to less inertia in the system when you fire in F/A.

[renegadecow]

On the FA having a slightly higher fps reading than Semi, I remember some time ago about a discussion where the conclusion (if it can be called that) was this:

 

On full auto, with the motor running continuously, the sector gear is spun with higher kinetic energy which causes the piston to be drawn back ever so slightly farther and increasing piston stroke. This increases the potential energy of the spring upon release and a small increase in fps is observed.

[amateurstuntman]

Could be, that would equate to the piston going about an extra 2/3 the thickness of a tooth.

 

My setup is an M130 short stroked by three teeth with a lightened piston so I would have thought it would have minimised that effect.

[Harmless]

Oh for gods sake lock this thread! faster spinning sector gears! suddenlt the piston is thrown back against a tensioned spring to steam forwards faster or for a longer travel! The explanation is more likely to be that way the chrono works. It is not going to be giving the individual fps of each bb on fully auto. God knows whats going on. Theories on how heavier bbs have more muzzle energy or velocity. The entire system is very simple spring provided equal energy to both weights of bbs, inertia of heavier bb is greater and therefore overcomes air resistance for longer than one with lower inertia = longer more stable flight.

[MDK_Marshal]

Oh for gods sake lock this thread! faster spinning sector gears! suddenlt the piston is thrown back against a tensioned spring to steam forwards faster or for a longer travel! The explanation is more likely to be that way the chrono works. It is not going to be giving the individual fps of each bb on fully auto. God knows whats going on. Theories on how heavier bbs have more muzzle energy or velocity. The entire system is very simple spring provided equal energy to both weights of bbs, inertia of heavier bb is greater and therefore overcomes air resistance for longer than one with lower inertia = longer more stable flight.

 

Wow. First, thanks for supporting my desire to have this thread closed, but good god you have no idea what you're rambling about.

 

Firstly:

 

"The explanation is more likely to be that way the chrono works. It is not going to be giving the individual fps of each bb on fully auto."

 

You have no idea how a chrono works, obviously, or you'd notice how stupid that sounds. The chrono is capable of accurately measuring the time taken for a projectile moving a couple of hundred miles per hour to break two light gates, and doing a sum that takes a fraction of a second to do that's so small it's not worth bothering about.

 

It's CERTAINLY capable of measuring the velocities of numerous shots, and storing them to some RAM. I'm pretty sure there's quite a few chrono's that can record FA velocities, and read back the velocities measured. At the very least there exist chrono's that'll give you an average of the values, which implies that values are stored somewhere and somehow, and as such, that it can get velocities for X BB's a second.

 

Secondly:

 

"The entire system is very simple spring provided equal energy to both weights of bbs"

 

You seem to have conveniently ignored the fact that numerous people have, in numerous situations and on numerous occasions, shown that a heavier BB Does indeed have more energy.

 

Does decent, verifiable experimental data mean nothing to anybody?

 

 

 

Seriously, lock this thread. PLEASE. The amount of people who believe that they alone must be right and are dead-set that the minority of people saying otherwise (even though that minority is RIGHT) could never, ever be wrong.

 

Again. Scientific process is weeping in the corner. Threadlock. please.