.2 or .25 bb?

[glfgmoney]

im not sure if there are limits over there in the Uk for most of u guys...but i know that between .2 and .25 there is a definite change in fps but it is much more painful when shot with a .25 bb...however my true question is whether or not a .25 will cause more stress or damage to your gearbox using a 1J spring compared to using a .2?

 

Also, will the rate of fire change if a heavier bb is used?

[Guges Mk3]

"...however my true question is whether or not a .25 will cause more stress or damage to your gearbox using a 1J spring compared to using a .2.."

 

In short the answer is no.

 

The answer to your question lies in the concept - Inertia.

 

Inertia

 

The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in motion to stay in motion in a straight line unless acted on by an outside force.

 

I heavier bb takes more energy -> force to get it moving due to Inertia. But, it does not stress your box directly. Now if you plugged your AEG up with a BB jam, regardless if its .20 or .25 it "will" stress your mechbox...because the BB is jammed.

 

Also, will the rate of fire change if a heavier bb is used?

 

Again - No.

 

ROF has nothing to do with the target mass you want to move - the bb. ROF is going to be completely based on your Spring (how heavy it is and the force to wind it back), Motor(the strength of the motor to wind springs), Voltage(the power available for the motor to wind a spring back) and Gears (the ratio that allows a motor to work in winding a spring back)...in that order.

 

It will fire at the same ROF, but the bb's will not go as far, when the bb weight increases.

 

Think of it this way, ever flick dried beans with your finger? You can flick them as fast as you can move your fingers. The small green beans flick pretty far, but when you flick the larger kidney beans they don't go as far. Your flicking rate hasn't changed...but the big beans just don't go as far due to "inertia"

 

And all the factors that determine the inertia factor are - mass, friction and speed.

[macabre]

The person who started this topic, obviously, has no idea at all how a aeg works.

 

THANKS

[shadow]

Guges Mk3 very good post +1

[FUmiYAsu]

I heavier bb takes more energy -> force to get it moving due to Inertia.

 

One thing was not quite clear. A heavier bb doesn't really take more energy, it takes more energy if you want to move it at the same velocity.

 

In your case, you will be using the same spring. Hence the same amount of spring energy would be stored in the spring when pull back. Therefore, the amount of energy that gets transfered to kinetic energy of the bb remains the same. The heavier bb just move slower.

So, the energy output is the same with both bb.

 

Just the fact that you need more force to move the heavier bb means more resistance for the gearbox and so it actually increases the stress by a really small tiny amount. But it's so tiny that it's not going to do anything.

[Svittidiu]

It's nearly the same wether you use .20g or .25g BB's.

[MGV101]

Think of it this way, ever flick dried beans with your finger?  You can flick them as fast as you can move your fingers.  The small green beans flick pretty far, but when you flick the larger kidney beans they don't go as far.  Your flicking rate hasn't changed...but the big beans just don't go as far due to "inertia"

 

And all the factors that determine the inertia factor are - mass, friction and speed.

<{POST_SNAPBACK}>

sorry about this but the way you are expaining intertia is wrong (or should I say half right?).

Yes indeed, inertia is the tendency of a body to resist acceleration but first you'll have to understand the physics definition of acceleration. Acceleration simply means change of speed. ie. the slowing of a BB bullet is also called acceleration.

 

A heavier BB is harder to move for the gun so it will initally travell slower than a lighter BB but at the same time, it is harder to slow down (by the air resistence)! In theory, both BBs would travel for the same distance as the same amount of energy was put into it initally. In reality, a heavier BB will travel a shorter distance but this is NOT due to inertia. The distance your BB will travel depends on three factors.

 

The energy you put in, the air resistance and wind, and the gravitional pull. Since BBs are the same size and is fired from the same gun, the air resistance and intial power is the same. The only difference is the gravitional pull. There will be a heavier gravitional force on the heavier BB so it will drop faster. (yes, everyting falls at the same speed in a vacuum during free fall but when there is an atmosphere and the BB is moving, gravity will have a greater effect on the denser object).

 

As a conclusion, the heavier BB is falling faster due to gravity not intertia!

oh, and why a kidney bean travel a much shorter distance? Cauz of air resistance! It is less dense and has a larger surface area for air resistence. If I were using your analogy, I could flick a small piece of cotton acorss miles as it is so light!!!

 

yes, hop up does also play a role in the distance of the BB too although I did not mention it eairler. The spin actually disrupts the air flow around the bb creating a slightly higher pressure at the bottom of the BB and a slightly lower pressure on top of the BB lifting it and countering the force of gravity (much like an airplane).

 

oh, and all the factors that determine the inertia factor are - mass, mass and mass!

[FUmiYAsu]

Actually, with the same energy input the heavier object will travel slower. KE = 1/2(mv)square

Hence, slower muzzle velocity. The effect of gravity have to a object 0.05g heavier is very small, almost no difference. hence the drop at almost the same rate. therefore the same "in air" time. but the heavier object travels slower, so in the same length of time, the heaver bb travels shorter distance before it reach the ground.

And so, it's not due to gravity and they will not travel the same distance with the same amount of energy input.

 

however, it is true that the heavier bb retains it's momentum better but this gain in distance travelled is not inversely proportional to the loss in distance travelled due to slower muzzle velocity. Therefore, they will not travel the same distance with the same energy input.

[Bob]

the .25 shud be a tad (hardly noticable) more sturdy/accurate in flight, it shoulnt be affected by the wind as much as a .20.

but it should not affect your gun, after all .20 to .25 is a very small increase.

 

Bob

[FUmiYAsu]

the .25 shud be a tad (hardly noticable) more sturdy/accurate in flight, it shoulnt be affected by the wind as much as a .20.

but it should not affect your gun, after all .20 to .25 is a very small increase.

 

Bob

<{POST_SNAPBACK}>

 

Tht's actually the most useful post here....

 

my posts were all on physics but doesn't really answer the question

[Bob]

cheers, all the rest were really long n boring, i didnt really get wat was been said

 

Bob

[DarkLite]

Well put.

 

The effect of gravity is so small as to be negliable.

 

However, with the same Energy input (Potential Kinetic Energy in the spring) the heavier bbs will not travel as fast.

[MGV101]

Actually, with the same energy input the heavier object will travel slower. KE = 1/2(mv)square

Hence, slower muzzle velocity. The effect of gravity have to a object 0.05g heavier is very small, almost no difference. hence the drop at almost the same rate. therefore the same "in air" time. but the heavier object travels slower, so in the same length of time, the heaver bb travels shorter distance before it reach the ground.

And so, it's not due to gravity and they will not travel the same distance with the same amount of energy input.

 

however, it is true that the heavier bb retains it's momentum better but this gain in distance travelled is not inversely proportional to the loss in distance travelled due to slower muzzle velocity. Therefore, they will not travel the same distance with the same energy input.

<{POST_SNAPBACK}>

Yes, indeed it is not proportional but it was close enough to treat it that way for simplicty's sake as it will be way to complicated to be posted in a forum if all factors was considered. It would depend on many factors and the gain from the momentum could be much more or much less than the muzzle speed depending on the situation.

 

There was an article on this site comparing the difference between a 0.2 and 0.25BB and from this graph http://www.arniesairsoft.co.uk/articles/fp...es/image003.gif the 0.25g BB has actually caught up with the 0.2g BB in just slightly over 0.5 seconds. If the air time of the two bullets are the same, the 0.25g BB will be travelling further than the 0.2g and the momentun gain is actually large than the loss of muzzle speed.

I never tested this myself but looking at what everyone had posted a heavier BB will travel a shorter distnce so the air time must be shorter. An 0.05g increase in weight IS significant for a BB if you look at its realitive mass. It is actually a 25% increase in weight for a 0.2g BB.

 

The effective distance between an 0.2 and 0.25 BB will be different depending on the power of your gun the barrel length, air pressure and a many many more factors and which bullet will travel further will depend on these situations.

 

The physics behind it is far too complicated to be discussed simply in a forum. Hell, I mean even air resistance would vary when the bullet change in speed and various forumlas would need to be worked out.

All I could say is, the answer does not simply lie in inertia. Inertia is no where close to the answer as a change in inertia could increase or decrease the distance depending on the situation.

[FUmiYAsu]

Yea, I agree tht just talking the theory without doing accurate testing is no good....

need to make one thing clear thou is I was only sayin tht the 0.05g was not important in the gravity aspect but not the momentum aspect...as it's % difference tht's important in tht....

 

nice scientific discussion with you

[MGV101]

Yea, I agree tht just talking the theory without doing accurate testing is no good....

need to make one thing clear thou is I was only sayin tht the 0.05g was not important in the gravity aspect but not the momentum aspect...as it's % difference tht's important in tht....

 

nice scientific discussion with you

<{POST_SNAPBACK}>

Yes indeed it is always nice to share each other's thoughts even if we are disagreeing on something. Sadly, it often turns into a flame war. Luckily it didn't happen here

[Bob]

AA members take note, you would be wise to follow the example on this page...

 

Bob

[Azrael]

something else that hasn't been mentioned-

 

aegs have a standard amount of air ejected from the cylinder, this will propel different weights of bbs at roughly the same joules every time, no matter the difference in weight, BUT if it were a gas gun, the gas expands exponentially the longer the bb stays in the barrel, so a heavier bb puts up more resistance to the gas expansion, yet exits at a faster pro-rata'd (from weight slowing it down to how fast it SHOULD be going) speed than a lighter bb. and a longer barrel capitalises on this.

 

basically- M700 firing a .2g bb will fire at 500fps, so you would expect a .25g bb to be fired at 375fps (25%) slower velocity for it to have (roughly) the same joules on impact. The truth is that a .25 would fire at about 410fps, and a .3 would be about 385fps. each heavier ammo, being more and more powerful, carrying more momentum, joules, impact power or whatever you want to call it. An AEG tuned to fire at 1 joule would happily fire .25s, and maybe even .3s at the same power (1 joule) but a gas powered airsoft gun would get exponentially more powerful with each heavier bb.

 

(percentages and fps's may be off a little, but the physics works, and its been extensively tested to be the case in a gas rifle.)

[Boba_Fett]

aegs have a standard amount of air ejected from the cylinder

 

The amount of air depends on the cylinder used in the AEG. It is not equal in all AEGs.

[FUmiYAsu]

Didn't know tht Azrael, good info...