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Wierd question...

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Wierd question...

Unread postAuthor: Gun Freak » Tue Jun 29, 2010 2:43 pm

This might sound like a dumb question but I think there is some science behind it. Is the projectile forced out the barrel by pressure or is it the actual push of the air/gas? For example, the compound round has o-rings so it can form an almost airtight seal in the barrel, allowing the pressure in the barrel to force it out. But what about projectiles that aren't close to an airtight seal? For example an airsoft bb in a half inch pvc barrel. The bb goes very fast but it can't be from pressure expansion so it has to be from the push of the air/gas in the chamber... does anybody understand what I'm saying?
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Last edited by Gun Freak on Thu Dec 02, 2010 8:29 pm, edited 1 time in total.
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Unread postAuthor: jrrdw » Tue Jun 29, 2010 2:55 pm

Well from how I'm understanding your question, I say it's from the gasses expanding if it's a combustion. If it's a pneumatic it's from a push of stored air massed/compressed into a storage chamber.
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Unread postAuthor: Gun Freak » Tue Jun 29, 2010 3:00 pm

Well why I am asking is because when you fire a pneumatic at something like your hand it pushes really hard, but that is not from pressure expanding and forcing your hand out a confined space. Know what I mean?
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Unread postAuthor: jrrdw » Tue Jun 29, 2010 3:06 pm

With a pneumatic your releasing stored air. There will be more input on this from different views, hang in there.
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Unread postAuthor: SpudBlaster15 » Tue Jun 29, 2010 3:44 pm

Acceleration is a result of a net force in the forward direction acting upon the constituent matter of the projectile, which of course has mass. Mathematically, it's defined as:

a = F/m

The net force on the projectile is a result of pressure acting upon the round's cross sectional area. This is expressed as:

F = PA

In simple terms, it's the pressure on the back of the projectile that causes it to move. Most of the applied force is a result of system pressure (The pressure in the chamber, valve, and barrel volume behind the projectile), but the inertia of the gas flow (What you refer to as the "push") does have an effect. This effect is more significant with lightweight projectiles, such as the airsoft round in your example.

A projectile does not need to form an airtight seal in the barrel to be propelled by system pressure. So long as the airflow into the barrel exceeds the rate of leakage around the projectile, pressure will build behind it and act on the cross sectional area, creating a net force.

In short, it's both, but system pressure is more important.
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Last edited by SpudBlaster15 on Tue Jun 29, 2010 3:48 pm, edited 1 time in total.
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Unread postAuthor: spudtyrrant » Tue Jun 29, 2010 3:44 pm

Gun Freak wrote:Well why I am asking is because when you fire a pneumatic at something like your hand it pushes really hard, but that is not from pressure expanding and forcing your hand out a confined space. Know what I mean?
it is actually lol, the pressurized air expands and pushes on the air in front of it, i take it you know that air has mass, and mass moving at any velocity equals force, which is what you feel when you dry fire a pneumatic.
EDIT:@SB15 oh thx make my explanation look bad by actually giving formulas and being more detailed :stfu: lol
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Re: Wierd question...

Unread postAuthor: Ragnarok » Tue Jun 29, 2010 3:52 pm

Gun Freak wrote:Is the projectile forced out the barrel by pressure or is it the actual push of the air/gas?

There's no actual difference between these two! Pressure is simply caused by air atoms impacting on a surface - in other words, them pushing on it.
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Re: Wierd question...

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Unread postAuthor: Gun Freak » Tue Jun 29, 2010 3:53 pm

Thanks guys, that answered my question.
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Unread postAuthor: jrrdw » Tue Jun 29, 2010 5:25 pm

Gun Freak wrote:Thanks guys, that answered my question.


Oh no no no! That's not the way it works here at Spudfiles. We have to post 3 or 4 pages of the same thing said 25 different ways until a argument breaks out and I have to lock the thread... :P :roll:
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Unread postAuthor: Technician1002 » Tue Jun 29, 2010 6:21 pm

Gun Freak wrote:Well why I am asking is because when you fire a pneumatic at something like your hand it pushes really hard, but that is not from pressure expanding and forcing your hand out a confined space. Know what I mean?


Yes.
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Unread postAuthor: deathbyDWV » Tue Jun 29, 2010 7:40 pm

jrrdw wrote:
Gun Freak wrote:Thanks guys, that answered my question.


Oh no no no! That's not the way it works here at Spudfiles. We have to post 3 or 4 pages of the same thing said 25 different ways until a argument breaks out and I have to lock the thread... :P :roll:


Alright!!! Let's go for it!!! I think it's caused by global warming!!! :D


Now seriously, I've wondered this too. I already understood they it's generally the same thing but this helps me understand it more...
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Unread postAuthor: Gun Freak » Tue Jun 29, 2010 8:59 pm

jrrdw wrote:
Gun Freak wrote:Thanks guys, that answered my question.


Oh no no no! That's not the way it works here at Spudfiles. We have to post 3 or 4 pages of the same thing said 25 different ways until a argument breaks out and I have to lock the thread... :P :roll:


Hahaha might as well lock it now lol :roll: :wink: where's BoyntonStu :D

Edited by jrrdw, no text smaller then size 7 or "tiny" from the Font Size drop down menu.
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