After you pull the trigger

[bad timing]

Great read thank you

[ZRH]

Can anyone recommend some really good books on internal ballistics and on designing semi auto guns?
I have a pdf of Theory of the Interior Ballistics of Guns, by J. Corner.
(I just recently got it and havent read it yet, but it was recommended.)
Any other titles I should look for?

There is no light reading material on this. There are a lot of articles in the Journal of Applied Physics,
Fiser, M. and Popelinsky, L. Small Arms
Peter, H. Mechanical Engineering. PRINCIPLES OF ARMAMENT DESIGN
Hayes, J., T. Elements of Ordnance
lots of papers from these guys -> http://www.unob.cz

[TooTall]

Thanks, ZRH. I'll have a look for some of those titles.

[SlayerG2-1]

As I understand it...
According to Boyle's Law, in any closed system, volume and pressure of gas are inversely proportional. The gas system of the AR-15 is a closed system until the bullet exits the muzzle, at which time the pressure within the gas system rapidly drops to atmospheric. Gas port diameter really controls resistance of gas entering the gas tube, that is how quickly it allows the gas tube to fill and the gas to reach the carrier key (gas lag time). The volume in the system is dependent on barrel length and gas tube length because both of these allow for more room for the gas to expand...as the gas is given more room to expand, the pressure within the system decreases. In short, you cannot affect volume or pressure of gas without also affecting the other; they are not independent.

[Dirtyboy333]

As I understand it...
According to Boyle's Law, in any closed system, volume and pressure of gas are inversely proportional. The gas system of the AR-15 is a closed system until the bullet exits the muzzle, at which time the pressure within the gas system rapidly drops to atmospheric. Gas port diameter really controls resistance of gas entering the gas tube, that is how quickly it allows the gas tube to fill and the gas to reach the carrier key (gas lag time). The volume in the system is dependent on barrel length and gas tube length because both of these allow for more room for the gas to expand...as the gas is given more room to expand, the pressure within the system decreases. In short, you cannot affect volume or pressure of gas without also affecting the other; they are not independent.

Thats exactly what i was thinking....Their dependent upon one another. So, a smaller GP would delay the pressure build up which would result in less pressure throughout the time of pressurization when compared to a larger port???

[patrick sweeney]

There are more gas laws than just Mssr. Boyle's.

Yes, port size does matter, otherwise goofs with drills couldn't screw up otherwise properly-gassed rifles.

What the port size does, within limits, is act as a throttling aperture. a smaller port will delay pressurization, but the gas tube (the complete system) will reach full pressure, and quickly. The definition of work is "area under the curve." The delay may not have as much effect on work as you might think.

The system is just that: a system. you have a balance of pressure, onset time, gas expansion, dwell time, etc. Yes, you can change one of them, and the others will adjust, but you're just fiddling around on the margins.