Pressure v. Velocity

[jski]

This touches upon another thread I start awhile back. I'm looking at 41 Magnum data on Hodgdon's website:

BULLET WEIGHT 220 GR. SPR JSP
CASE REMINGTON
PRIMER WINCHESTER LP, LARGE PISTOL

Starting Load Maximum Loads
Manufacturer Powder Bullet Diam. C.O.L Grs. Vel. (ft/s) Pressure Grs. Vel. (ft/s) Pressure
Hodgdon H110 0.410" 1.580" 18.0 1,352 23,000 CUP 20.0 1,529 34,000 CUP
Hodgdon Universal 0.410" 1.580" 6.5 921 18,900 CUP 8.5 1,178 38,600 CUP


BULLET WEIGHT 245 GR. CAST LSWC
CASE REMINGTON
PRIMER WINCHESTER LP, LARGE PISTOL

Starting Load Maximum Loads
Manufacturer Powder Bullet Diam. C.O.L Grs. Vel. (ft/s) Pressure Grs. Vel. (ft/s) Pressure
Hodgdon H110 0.410" 1.630" 18.5 1,372 22,800 CUP 21.0 1,563 37,400 CUP
Hodgdon Universal 0.410" 1.630" 6.3 1,001 21,200 CUP 8.0 1,164 36,000 CUP

The pressures are in RED and the velocities are in BLUE.

If you look the 220 gr bullet using H110 v Universal, with a 13.5% decrease in pressure, I get a 30.0% increase in velocity.

If you look the 245 gr bullet using H110 v Universal, with a 3.9% increase in pressure, I get a 34.28% increase in velocity.

You would think that these small percentage changes in pressure wouldn't result in such large velocity differences? Is there something about the pressure curve? Hell, with the 220 gr bullet there's a decrease in pressure and a significant increase in volocity???

 

[mcb]

It's not the peak pressure but sum of the area under the pressure vs distance/time curve that determines the kinetic energy/momentum change of the projectile. They rarely publish that curve just the peak since it's the peak pressure that breaks things usually.

 

[jski]

It's not the peak pressure but sum of the area under the pressure vs distance/time curve that determines the kinetic energy/momentum change of the projectile. They rarely publish that curve just the peak since it's the peak pressure that breaks things usually.

So Universal is harder on you gun than H110, the magnum powder ... for the 220 gr bullet?

 

[mcb]

So Universal is harder on you gun than H110, the magnum powder?

As long as you are staying at or under the pressure the gun was designed for (usually that is based on the SAAMI specs for the cartridge) you probably won't see much difference in wear.

 

[jski]

As long as you are staying at or under the pressure the gun was designed for (usually that is based on the SAAMI specs for the cartridge) you probably won't see much difference in wear.

Looking at 357 Magnum data I see the same thing.
Seems like Universal is a bad deal? Same wear but much less velocity.

 

[GeoDudeFlorida]

Looking at 357 Magnum data I see the same thing.
Seems like Universal is a bad deal? Same wear but much less velocity.

IF maximum velocity was the only variable involved that would still be wrong. Look at the totality of the combustion process and the total number of variables involved and you will quickly stop trying to summarize all of ballistics in terms of only one variable. Oversimplification is almost as dangerous as over-complication. Don’t believe me? Then answer this: why bother with blended nitrocellulose when pure nitroglycerin yields so much more energy?

 

[jski]

IF maximum velocity was the only variable involved that would still be wrong. Look at the totality of the combustion process and the total number of variables involved and you will quickly stop trying to summarize all of ballistics in terms of only one variable. Oversimplification is almost as dangerous as over-complication. Don’t believe me? Then answer this: why bother with blended nitrocellulose when pure nitroglycerin yields so much more energy?

Ok, I’m willing to go with that. But tell me the advantages to using Universal v. H110. Why would I prefer Universal over H110?

Of course, this also applies to other similar powders.

 

[FROGO207]

Universal burns quicker and thus spikes pressure sooner and pushes the bullet out sooner but trails off faster. Slower propellants build pressure slowly and push slowly for a longer period to gain speed. You use less of a more energetic propellant to get the bullet up to speed but it does not sustain that push as long as one that burnes slower.

 

[jski]

Universal burns quicker and thus spikes pressure sooner and pushes the bullet out sooner but trails off faster. Slower propellants build pressure slowly and push slowly for a longer period to gain speed. You use less of a more energetic propellant to get the bullet up to speed but it does not sustain that push as long as one that burnes slower.

Good points, especially for shorter barrel handguns. But would I actually get a greater velocity out of a 3” barrel from Universal?

 

[FROGO207]

Most of the pressure/burn are over in the first inch or so of bullet movement at the beginning of combustion. With a revolver there is some escape due to the cylinder/barrel gap. With a longer barrel and a slower burning propellant there is more "push" to be able to overcome friction. Eventually if the barrel is long enough the projectile will slow due to that continued friction.

 

[GeoDudeFlorida]

The secret of steel is not its hardness but it’s elasticity. It stretches and deforms under stress, then returns to its original form and shape - mostly. Heat, time, wave fronts and constriction alter the ability of steels to return to shape. Consider the combustion process: it begins in tiny cavity and grows beyond the confines of the barrel and chamber. That’s why different powders with different properties deliver different results. It’s not a puzzle or a riddle it’s mechanics.
Now, answer the previous question: Why bother with blended nitrocellulose when pure nitroglycerin yields so much more energy?
There’s a good answer but it’s too simple to accept if you’re just told what it is and too complicated to be obvious.

 

[mcb]

Most of the pressure/burn are over in the first inch or so of bullet movement at the beginning of combustion. With a revolver there is some escape due to the cylinder/barrel gap. With a longer barrel and a slower burning propellant there is more "push" to be able to overcome friction. Eventually if the barrel is long enough the projectile will slow due to that continued friction.

Peak pressure happens with the first inch or so of the bullets travel down the barrel but the propellant should still be burning most of the length of the barrel and in some cases you only burn about 80-90% of it in the barrel. H110 is a classic example of a powder that does not fully burn in most handgun length barrels and as a result you get some spectacular fireballs from H110.

The 220gr bullet, 20gr of H110, from an 8-inch gun only burn about ~80% of the powder. Peak pressure happens after the bullet has traveled roughly 3/8 inch. Based on a quick check in Quickloads.

There is also a thread currently active on here where MDT made a 69 inch long barrel for a 308 and the bullet was still accelerating down that barrel. It should in theory be possible to make a barrel long enough to stop a bullet but it practice that is a silly length of barrel, much sillier then MDT, for most centerfire cartridges.

 

[Walkalong]

Ok, I’m willing to go with that. But tell me the advantages to using Universal v. H110. Why would I prefer Universal over H110?

Of course, this also applies to other similar powders.

Different speeds for different tasks in .44 Mag. H-110 is for full power max velocity loads, while Universal won't get there because it is too fast. It will however, work very well for midrange loads, where H-110 will not.

 

[barnfrog]

Why would I prefer Universal over H110?

Maybe because you get twice to three times as many rounds from a pound of Universal than you do from a pound of H110?

 

[jmorris]

Hell, with the 220 gr bullet there's a decrease in pressure and a significant increase in volocity???

Well, we know the curve isn’t linear. Then you throw in data collected at different times, with different environmental conditions, maybe even with different equipment, maybe even types of collection (burst disk, strain gauge, etc). It’s no wonder load manuals post two different max/mix for the same combinations.

 

[someguy2800]

Ok, I’m willing to go with that. But tell me the advantages to using Universal v. H110. Why would I prefer Universal over H110?

Of course, this also applies to other similar powders.

Economy and greatly reduced recoil.

 

[AJC1]

A fast powder downloads a lot better but will peak fast and still opterate the bullet. The slower powder will give more velocity in heavier bullets because the curve is stretched out longer down the barrel. Fast powders are efficient at moving light bullets and don't need full pressure for a more complete burn. 4227 is a great powder to learn with about required pressure. A fast powder is more power dense so it will always be more efficient. You want to use the fastest powder that gives the required velocity without going over pressure.

 

[jski]

Guys, I would think that a magnum H110 load that breaks your wrist puts more wear on the gun than a mild Universal load that produces a higher peak pressure?

 

[lordpaxman]

And your wrists….
I’m not quite sure what you’re trying to deduce. I own a 686 and shoot both .357 and .38’s in it. The .38’s are mild, the .357’s are stout. I’m sure the .357’s produce more “wear”, but the gun is designed for them. Given there’s no material defect I’m pretty sure I won’t wear out the gun.

 

[Walkalong]

Guys, I would think that a magnum H110 load that breaks your wrist puts more wear on the gun than a mild Universal load that produces a higher peak pressure?

If you don't want full magnum loads, yes, a medium (medium fast) speed powder like Universal is better suited. BE-86 would be a fine choice.

If you can get the burn speed/pressure curve down in your head it will make sense.

 

[someguy2800]

Pretty sure if you shot 100,000 rounds in a revolver, or just shot 100,000 blanks you would put about the same amount of wear on it. Just shoot it.

 

[jski]

And your wrists….
I’m not quite sure what you’re trying to deduce. I own a 686 and shoot both .357 and .38’s in it. The .38’s are mild, the .357’s are stout. I’m sure the .357’s produce more “wear”, but the gun is designed for them. Given there’s no material defect I’m pretty sure I won’t wear out the gun.

Let me ask it this way: The velocity the bullet leaves the barrel determines the recoil and not the peak pressure. And aren’t the tresses/forces that cause wear in a gun the same forces that cause recoil? Peak pressures do test the material integrity of the cylinder, assuming it’s a wheelgun, but that’s different from wear?

Just trying to get an idea of some of the considerations involved in selecting a powder. And Universal and H110 represent 2 ends of the spectrum, sort of.

 

[someguy2800]

Let me ask it this way: The velocity the bullet leaves the barrel determines the recoil and not the peak pressure. And aren’t the tresses/forces that cause wear in a gun the same forces that cause recoil? Peak pressures do test the material integrity of the cylinder, assuming it’s a wheelgun, but that’s different from wear?

Just trying to get an idea of some of the considerations involved in selecting a powder. And Universal and H110 represent 2 ends of the spectrum, in a fashion.

It’s not just the bullet. The powder mass is also being ejected and contributes to recoil.

https://shooterscalculator.com/recoil-calculator.php

I don’t believe that it’s accurate to say recoil produces wear. The only part in a revolver that moves during firing is the hammer. All the action parts only move between firing, so simply advancing the cylinder, moving the cylinder lock, and recocking the hammer is what will wear those parts out, regardless of if you even shoot it or not. You can get flame cutting or even splitting on the forcing cone from a steady diet of full loads.

I’ll tell you this, shoot a cylinder full of universal loads, and a cylinder full of H110 loads and your going to know right away which one you want to shoot a steady diet of. According to the load data you posted for the 245gr bullet, the universal load will produce 12 ft lbs of recoil, and the H110 load will produce 27

 

[Czy_Horse]

To check out the difference in pressure curves, there's Gordon's Reloading Tool.
I used a 6" barrel for example with both powders.

H110, not all the powder is burnt before bullets leaves barrel


Universal, powder load is totally burnt well before bullet exits barrel.

 

[jski]

Gordon's Reloading Tool? Never heard of it but a quick web search turns up some very promising reviews!
Gordons Reloading Tool (GRT), How to Start Using