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Old February 3, 2013, 07:38 AM   #1
Delmar
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BP pressures vs Smokless

I am trying to understand the supposed great difference in pressure between similar weighted bullets in black powder and smokeless loads. For example, if you loaded a 200 grn bullet in a 45 acp cartridge with a smokeless load that achieves 900 ft/second, how is the resulting pressure not virtually identical to loading a 200 grn conical in an 1858 Remington with enough BP to achieve 900 ft/second?
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Old February 3, 2013, 08:13 AM   #2
salvadore
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I doubt you could get enough BP in a 45acp case to achieve 900fps with a 200gr bullet.
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Old February 3, 2013, 08:22 AM   #3
Doc Hoy
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What is the effect of ....

...The length of the barrel of the .45 ACP (Five inches for the .45 Auto) which achieves 900 FPS in comparison with the barrel length of the 58 Remington (7.5 to 8 inches)?

Bullet accelerates for a longer period of time in the longer barrel. Therefore to achieve the same speed, less pressure is required.

My 5.5 inch Remington won't push a round ball (154 gr) to 900 FPS. IIRC it tops out about 650.

I can get close to 900 in my 5.5 inch Vaquero (200 gr .45 long colt with as much powder as I can stuff into it - about 35 to 40 grains.) but that has the additional variation of the crimp on the case.

I think the way that works in smokeless powder is, Crimp it heavy - increase the speed, crimp it light, decrease the speed. IIUC, the crimp permits pressure to build up before the bullet begins to accelerate. More crimp equals more pressure build up and hence, faster acceleration in the barrel.

In the Remington, what you have holding the ball in place is the tightness of the fit of the bullet in the chamber. That might be followed by a build up of pressure as the ball transitions from the chamber to the forcing cone.
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Old February 3, 2013, 08:48 AM   #4
Delmar
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Quote:
Originally Posted by salvadore
I doubt you could get enough BP in a 45acp case to achieve 900fps with a 200gr bullet.
Bullets don't seat as deep in a 45 acp case as they do in a cap and ball cylinder, but you may be right. It might take 45 lc to make a completely accurate comparison.
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Old February 3, 2013, 09:05 AM   #5
Delmar
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Quote:
Originally Posted by Doc Hoy
...The length of the barrel of the .45 ACP (Five inches for the .45 Auto) which achieves 900 FPS in comparison with the barrel length of the 58 Remington (7.5 to 8 inches)?

Bullet accelerates for a longer period of time in the longer barrel. Therefore to achieve the same speed, less pressure is required.

My 5.5 inch Remington won't push a round ball (154 gr) to 900 FPS. IIRC it tops out about 650...
Your response sent me over to ballistics by the inch

a Cor Bon 200 gr. JHP +P will reach 1102 ft/sec in a 6" barrel and 1150 in an 8'' barrel. It is enough difference to pay attention to but not a huge difference.
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Old February 3, 2013, 09:09 AM   #6
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My recollection dovetails with yours...

When I was still active duty, we shot .45 1911. It was a 150 grain Ball style projectile. In the Navy that meant Round Front.

1100 fps was the advertised MV.
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Old February 3, 2013, 09:31 AM   #7
Mike Irwin
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A lot of it can be the result of the pressure curve.

Black powder burns at a constant rate, and rather quickly. All of its push is done early in the bullet's travel down the barrel.

Smokeless powder, however, being progressive burning, has a much longer burn time, and depending on the initial chamber pressure, much different burn characteristics.

Smokeless powder will have a much longer pressure curve, meaning that it will keep pushing on the bullet for a much longer time.
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Old February 3, 2013, 04:32 PM   #8
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Pardon me for veering slighly off topic but I thought some of you may enjoy this.

Back in 1968 I worked in the Chrysler test and development labs in Highland Park Michigan. One of the projects we worked on were air bags. At the time it was just a project to determine if they were even feasible. The state of the art systems of the day utilized a compressed gas in a bottle with a diaphragm seal and electromechanical system to rupture the diaphragm and allow the gas to escape into the bag when an impact was sensed. Chrysler engineers sought to develop something cheaper and easier to build and decided on generating the gas for bag inflations by rapidly burning a fuel. Without getting into the weeds suffice it to say that gunpowder became the initial fuel of choice. Because smokeless generates so much more gas for a given volume than BP and is very sensitive to pressure, it did not take but a few 'booms' to determine BP was a better choice. The earliest "gas generators" we made were filled with BP collected by cutting shotgun shells open, and ignited by using flash bulbs with the glass bulbs removed as detonators that ignited the powder with battery current sent by the impact sensor. I am sure you can imagine the smoke we made when the bag broke, which was quite frequently.

As time went on more sophisticated fuels were developed by outside chemical vendors and (I believe) today all air bags in modern cars use a gas generator that burns a fuel and fills the bag with the gas produced in only a few milliseconds after impact. Think about that when you get behind the wheel next time. The exact same stuff we like to burn in our pistols and rifles was instrumental in developing the air bag in front of you.
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Old February 3, 2013, 04:44 PM   #9
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Where were you getting shotgun shells in 1968 that were filled with black powder?
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Old February 3, 2013, 04:57 PM   #10
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robhof

I can answer the B/p shot shell question; growing up in a small town in the 60's I remember the local hardware stores carrying B/p shot shells for damascus barrels, of which many were in current use at that time.
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Old February 3, 2013, 05:10 PM   #11
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We bought them at hardware stores and gun stores. That was 45 years ago. It was a different time.
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Old February 3, 2013, 05:40 PM   #12
NoSecondBest
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Quote:
We bought them at hardware stores and gun stores. That was 45 years ago. It was a different time.
Doesn't sound that long ago to me. I was in the service back then. I was big into shotgun shooting back then (still am) and I don't remember seeing any black powder shotgun shells being sold. I guess someone could have had some stashed away in some out of the way store or something. Kind of sounded like it was easy to find the way you were describing it. Back then, it was pretty difficult to even get black powder. I had to get an explosives license just to buy what I wanted to use for my muzzle loading guns. Got easier to get a few years later when Thompson Center started selling their line of muzzle loaders and a lot more shooters go into the game. They lifted the requirement of having to have an explosives license and just limited how many pounds you could get at one time.
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Old February 3, 2013, 07:01 PM   #13
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We are not talking large quantities here. One bag could be inflated with the gas from maybe two shells and we may have detonated only a couple of bags a week with black powder and the rest with vendor supplied gas generators. Each test was recorded with high speed photography and data recorders and the analysis of the data obtained was time consuming. There were no laptops to crunch numbers with. There did not seem to be any difficulty obtaining the shells. They always had a supply. Since explosives were not allowed anywhere inside the Engineering complex so they built a small building on some vacant land they owned and did all the loading and storage in that building.
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Old February 4, 2013, 11:14 AM   #14
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I have loaded, for experimentation only, a 45 ACP and 7.62 X 39mm rounds by filling the case with BP (or Pyrodex) and then seating the bullet. It did fire, but velocity was low. At least I know it can be done from personal experience, but probably not recommended...FWIW
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Old February 4, 2013, 12:20 PM   #15
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The difference bp & smokeless

@ Delmar:

BLACK POWDER is easily ignited, makes a lot of smoke and leaves much of a residue in the barrel.

Normal load of black powder of about 4.5 grams for a shotgun 16 ga makes about 400 bars pressure.

The pressure created is somewhat lesser in the chamber and steadily progresses and increases by the end of barrel which is the reason for louder gunshot, and stronger recoil when compared to modern smokeless powder.
Increasing the amount of black powder load proportionally increases the pressure in the barrel – proportionally as well. Roughly for 1 gram of load increase the pressure will increase for about 100 bars. For this reason black powder can be measured by standard volumetric measures. It can also be used in bullet casings without stiffeners. Due to various production types the package instructions must be followed. To be stored in airtight packages, the best in dark bottle in cool and dry place. Very sensitive to moisture.

THE DIFFERENCE – SMOKELESS POWDERS:
Harder to ignite, no smoke and minimal residue in barrel!

At open space, burns slow and uniformly and makes almost no smoke. It is harder to ignite when compared to black powder. For this reason only special ignition caps can be used AND NOT black powder ignition caps.
For comparison:
Smokeless powder load for 16ga shotgun in amount of 1.80 grams makes pressure of 500 bars.
Black powder load for 16ga shotgun in amount of 4.50 grams makes 400 bars pressure.

Increasing the load weight of smokeless powder will make progressive increase of pressure in the barrel. So, incresing the same load by 0.50 grams will make the barrel pressure to about 1000 bars, and increasing the load by 1.0 gram gets to 3500 bars. For this reason it is not recommended to make volumetric measures, but to use precise weight scale because the smallest error can lead to explosion of barrel and to personal injuries.

When compared to black powder, the smokeless powder makes the highest pressure in the bullet chamber and slightly decreases to the end of barrel, This makes less loud gunshot, and softer recoil.

Each type of smokeless powder may differ in specific weight and must be loaded as per makers instructions to avoid accidents.
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Old February 4, 2013, 12:34 PM   #16
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Last year, one guy bought a brand new 9 mil semi-auto pistol, and full reloading equipment.

He filled up 9 x 19 mm casing full of smokeless powder thinking the size of casing really is the measure to load. He was not using any other measure, nor scale.

He came to our local range, to test and fired at 25 meter target.

As a result, the slide of modern 9 mm pistol came back to his head and gun destroyed.

Hospital treatment followed. He survived. The gun did not.

Lessons learned..... well, you got it!
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Old February 4, 2013, 12:38 PM   #17
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Maybe this will help, graphing the difference between the two. Look at the charge weights!
Muzzle velocity is identical as is bullet weight.
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Old February 4, 2013, 03:14 PM   #18
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@ Jolly1,

I have loaded .45 ACP with a full case of Pyrodex (compressed charge of roughly 37 grains) and the pistol cycled fine, although the report was lower and recoil was lighter.

Same thing with 7.62 X 39mm.

Keep in mind that many smokeless powders, such as Hercules Bullseye, take very little powder (by volume) to do the job and it is possible to double and perhaps even triple charge a case...
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Old February 4, 2013, 03:28 PM   #19
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Quote:
I have loaded .45 ACP with a full case of Pyrodex (compressed charge of roughly 37 grains) and the pistol cycled fine, although the report was lower and recoil was lighter.
Its a hoot seeing all that smoke oozing out of every nook and cranny of a 1911.
You can triple charge a .45 ACP with W231 and still seat a bullet.
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Old February 4, 2013, 03:29 PM   #20
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It gave new meaning to the term 'smokewagon...'
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