Going back to the original post, the question is, when I replicate the components in the book, does muzzle velocity indicate pressure? The answer is, it does, and very well.Velocity changes are an indicator of pressure changes. But they are a poor indicator of actual peak pressure.
I have experienced this as well, I always take it a a sign to stop. No sense in wasting powder, if you need more speed, might be time for a different powder.^^^Yep. What I have found with my handgun reloading, is there is a point where dumping more powder in a case is a diminishing return. When developing loads, there always seem to be a point where adding more powder does not mean significant increases in velocity.
In that sense yes, it can be very helpful.If you have the same length barrel as the book, and are using the same components, and are getting book MV, you are also getting book pressure. I have made many measurements of pressure and velocity over the years, and this holds up very well.
I havent been reloading near as long a lot of guys here but I dont know if I have ever used all of the listed components let alone had the same firearm as used in the test.Going back to the original post, the question is, when I replicate the components in the book, does muzzle velocity indicate pressure? The answer is, it does, and very well.
Further, peak pressure is very highly correlated with the area under the pressure curve. MV is well correlated with both total pressure and peak pressure.
If you have the same length barrel as the book, and are using the same components, and are getting book MV, you are also getting book pressure. I have made many measurements of pressure and velocity over the years, and this holds up very well.
And peak pressure doesn’t necessarily correlate well to average pressure (area under the curve).
But it does, at least if you are sticking to the question posed in the OP.
The length of your barrel is fixed. The integral of pressure over distance is the work done to accelerate the bullet.
You get more area under the curve by increasing the peak.
Total area under the curve is very highly correlated with peak pressure.
You get more area under the curve by increasing the peak.
It’s been 20 years since Calculus III, but I thinks it the double integral of the pressure curve to find the area under the curve. Maybe?
I think we are looking at the situation differently. You've seen good correlation between peak pressure, average pressure, and velocity from a specific set of components in a specific firearm. I believe that.But it does, at least if you are sticking to the question posed in the OP.
Can we extrapolate that if we reach this speed with our chronograph then we have reached max?
Say we had the exact bullet listed in the load which it doesn't specify, but for arguments sake, let's assume the exact bullet. We see that listed max for this bullet is 4.7 gr at 1140fps with a four inch barrel at specified oal.
bullseye!I also seem to remember that a higher peak doesn't always mean more area under the curve.
Good luck to those that try. However, that’s not what I use a chrono for. In regard to this thread, if I duplicate what the published load data has, and am under the velocity published, is there some confidence I am also under the published pressure and am operating in a safe range.I think that might be the worst thing about chronographs and published velocities with load data, people trying to achieve some written number.
I don’t have the capability to measure pressure. I can only measure velocity. With pistol, I’ve observed some high pressure signs (blown case web) and knew something was wrong, but wasn’t willing to test those loads with a chrono to see what the velocity was. The collective advice from this forum is that you’re over pressure limits by the time you actually see pressure signs. I really only want to stay safe!There is no better way to ensure reloading safety than to stay at or below published pressure tested data, with a corresponding absence of high pressure signs.
SAAMI does not just specify pressure. SAAMI also specifies velocity.
Given those constraints, if you are using the same type of powder and the same bullet mass as the book, muzzle velocity is highly determined by peak pressure.
The collective advice from this forum is that you’re over pressure limits by the time you actually see pressure signs. I really only want to stay safe!
SAAMI does not just specify pressure. SAAMI also specifies velocity.
keep an eye on your ejected brass. if factory ammo ejects brass six feet out and your reloads are ejecting brass 12 feet out, you may be over max pressure.
luck,
murf
then maybe i misunderstood newton's third law of motion. chamber pressure is the force that is acting on the slide. more pressure means more force applied to the slide which means more slide velocity. more slide velocity means a more forceful case ejection. a more forceful case ejection means the case lands farther from the gun.Ejection distance is a function of slide velocity which is a function of slide weight and various springs, not chamber pressure.
^^^Yep. What I have found with my handgun reloading, is there is a point where dumping more powder in a case is a diminishing return. When developing loads, there always seem to be a point where adding more powder does not mean significant increases in velocity.
1. He doesn't say when this experimentation took place so it's impossible to know if it was before or after Carpenter worked with Ruger to come up with the stronger steels.If he is blowing up guns at 70,000 PSI, he needs to use better steel for the cylinder.
Barring issues like rough or deformed chambers, the pressures were probably far higher than any of them thought they were. From the article:They all were loading Unique & heavy cast bullets. As the powder charges were increased, case extraction started to become harder.
John Linebaugh said:I have personally loaded hundred of rounds of ammo well over 60,000 psi and even 70,000 psi level in special test guns. In all cases I got normal extraction and normal looking primers. Scott Heter of Speer wrote me years ago of fired cases falling out of the chamber of pressure guns when the gun was tipped up. These loads exceeded 60,000 psi. Even with this high pressure the cases fell out of the chamber by gravity.
If you take the book velocity and adjust it to your barrel length, when you reach that velocity you are very close to the peak pressure that the test loads in the book generated. Seating depth, leade, brass thickness, and chamber tightness all influence pressure, it's true. But more or less pressure produces more or less muzzle velocity.
Bingo! While some of his other writings are somewhat dated, I default to Linebaugh on this subject. So-called pressure signs in revolvers can show up at any pressure level. Especially sticky extraction.Linebaugh did some experimentation with straight wall revolver cartridges and found that the traditional reloading pressure signs weren't a great way to gauge pressure in those cartridges.
"Straight cases handle pressure differently than bottle-neck cartridges and often show no excessive pressure signs. We have blown a few guns up here, on purpose, and in all instances upon recovery of the cylinder fragments and case remains, the primer has shown normal pressure. Pressures in these instances have run from 70,000 to over 100,000 psi in our estimation. Do not depend on case pressure signs for danger signs in a sixgun. In most cases the first sign of high pressure you will have, other than excessive recoil and blast, is a bulged cylinder or cracked bolt notch.”
Three points.If he is blowing up guns at 70,000 PSI, he needs to use better steel for the cylinder.
then maybe i misunderstood newton's third law of motion. chamber pressure is the force that is acting on the slide. more pressure means more force applied to the slide which means more slide velocity. more slide velocity means a more forceful case ejection. a more forceful case ejection means the case lands farther from the gun.
you can run these steps backward to understand that cases farther from the gun means more chamber pressure.
murf