Mike / Tx said:As mentioned pressure isn't going to get you velocity,
Are you sure? IME, adding powder always seems to increase pressure and velocity.
Mike / Tx said:As mentioned pressure isn't going to get you velocity,
This is a sound evaluation, with one quibble. Muzzle velocity is a function of integral pressure over the course of bullet travel down the bore, not average pressure.I would not assume that. As others have stated, pressure is measured in the chamber, and is not a function of barrel length. Peak pressure almost always occurs when the bullet has traveled down the barrel very little. It's also important to understand that there is no direct connection between peak pressure and velocity. Velocity is much more related to average pressure. (That's the extent of my knowledge. Somebody smarter than me can add on/clarify.)
I have and load ammo for a Glock 29 (and Glock 20). I just did a quick check of my chrono data and compared to the books (Speer & Hornady). My loads slightly exceed their posted velocities - even with my shorter bbls. This is a classic "your mileage may vary."
I don't have a lot of different loadings for the 10mm, as I consider it a utilitarian - rather than recreational - cartridge. But I'd be happy to share data if you believe it may be of assistance.
A little ruff weren't you
Are you sure? IME, adding powder always seems to increase pressure and velocity.
Are you sure? IME, adding powder always seems to increase pressure and velocity.
It is about the pressure curve, not the peak. A simple spike peak will get you nothing. An example of this woub be to (Don't really do it!!!!) Load a 338 Lapua with Accurate2. Burn however much powder it takes to hit SAAMI max pressure. I but you won't get 1200 fps velocity.Are you sure? IME, adding powder always seems to increase pressure and velocity.
It is about the pressure curve, not the peak.
At the macro level (and as a starter for those starting to grasp internal ballistics), this is a pretty good analogy.Consider this, think about a big, heavy door, say a safe door.....
Now, slap that door with your hand...slap it hard...
Besides making your hand sting, what happens? The safe door moves a little bit,,,maybe
Now, PUSH the safe door, and what happens, the door moves and as you keep pushing it gathers speed. The push isn't as "hard" as the slap, but it's duration allows the door to overcome the resistance of inertia and begin moving, slowly at first, then faster and faster as the push continues.
Consider the slap "peak pressure" and the push to be the continuous push over the full pressure curve.
The analogy isn't exact, but does illustrate the general principles.
No ... pressure is not measured in the barrel ... it is measured in the Chamber !I do understand the pressure is measured in the barrel but a shorter Barrel does not allow the pressure to build as it would in a longer Barrel before being released. I am not expecting the pressures or muzzle velocity to be by the book in the smaller Barrel that is a known
I must respectfully disagree with the bolded potion of the above statement.RKG said:Peak Chamber Pressure is the highest value that would appear on a graph of chamber pressure during bullet travel down the bore. Excessive Peak Chamber Pressure is what causes guns to blow up. Peak Chamber Pressure occurs at the point where propellant combustion ends, and depending on propellant speed, may be before the bullet begins to move or very shortly thereafter.
In fact, one of the keys to the so-called "short barrel" self-defense rounds most of the major ammo makers started offering about ten years ago is faster powders, with the goal being to have the pressure peak sooner rather than still be increasing when the bullet exits the muzzle.
As anyone who looks at the unburned powder kernels on the bench...the propellant clearly hadn't all stopped burning as soon as the bullet started to move.
You're not breaking anything to me -- I know that. But that's not what the statement to which I responded said.74A95 said:I hate to break the news to you, but pressure peaks way before the bullet has exited.
RKG said:Peak Chamber Pressure occurs at the point where propellant combustion ends, and depending on propellant speed, may be before the bullet begins to move or very shortly thereafter.
Any time you sweep up a little pile of the dust out in front of the firing line . . . you will find you can light it with a match, and it will flare like powder because there is a lot of unburned powder in it.