Just finished up an article that should help people gain a better understanding of the pressure at play in their firearms.
Let me know if you have any questions and I look forward to your comments!
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I think you may have misunderstood what I wrote there. I do not say that more powder gives less pressure. What I said was that there was less pressure available to act on the bullet, due to component expansion. The pressure is not lower, but rather is lost to case expansion. This very same behavior can be exhibited when forming AI brass. Moving the brass in such a way tends to absorb pressure.What would more powder give less pressure?
I think you may have misunderstood what I wrote there. I do not say that more powder gives less pressure. What I said was that there was less pressure available to act on the bullet, due to component expansion. The pressure is not lower, but rather is lost to case expansion. This very same behavior can be exhibited when forming AI brass. Moving the brass in such a way tends to absorb pressure.
My findings are easily reproduced and evidenced by the fact that over-pressure rounds tend to exhibit more case web expansion. If you perform similar testing, you will find that the cases measured at the point of velocity loss will be larger and exhibit less spring-back than cases fired before velocity loss.
I'm sorry, but the science behind this is quite settled.And yes, it makes sense that cases measured at the point of velocity loss will be larger but it still holds that you can't have one pressure exerted on the inside walls of the case and a different one on the bullet.
It makes sense that the pressure would be the same on all surfaces of the "container, except for the fact the bullet starts moving. I don't know how that affects things. It must start at the same pressure, and as pressure subsides, why would it not over all the surfaces, chamber, barrel, bullet.The pressure inside the case is going to exert exactly the same pressure on the bullet as it does on the case.
Indeed you are correct. However, if the "container" expands, the pressure is then reduced, which results in lower velocity.It makes sense that the pressure would be the same on all surfaces of the "container
A direct quote from the article:Rather than saying velocity falls off because pressure decreases (actually pressure is very high), it would be more accurate to say velocity decreases because pressure is relieved in ways other than the bullet moving down the bore.
It says the exact same thing that you are now saying. I'm sorry but I know of no other way to explain this to you, nor do I think any explanation I could provide would be adequate for you. I'll say no more on it.Velocity Loss
Excess pressure can be detected fairly reliably by use of a chronograph as well. If you are adding powder incrementally such as when doing an OCW load development process, yet rounds with more powder yield less velocity, this can be an indication that the brass has been pushed beyond it's limit. If it can not hold the pressure, then it will not constrict the volume adequately and will result in less pressure being exerted on the bullet. The pressure will be lost to component expansion internally. A fairly precise chronograph is required to be able to track this event, but it is noteworthy.
But isn't it reduced on all surfaces?Indeed you are correct. However, if the "container" expands, the pressure is then reduced, which results in lower velocity.
But isn't it reduced on all surfaces?
If the brass is not allowed to grab hold of the chamber walls, then all of that pressure is transferred rearward onto the base of the case, the bolt face, and subsequently the bolt lugs and action. If water is in between the brass and the chamber walls, even very light and mildly loaded ammunition will cause severe pressure signs. The ability of the brass to grab onto the chamber walls is paramount to the proper functionality of the firearm.
One part of it is definitely right, the brass must expand and seal the chamber from hot high pressure gases so they only escape down the barrel, and not through the action into our face.I disagree with this.