Reloading question

[918v]

What are you talking about? I'm talking about recoil which has nothing to do with pressure. You can have two loads using identical bullet weights, one generating more pressure than the other, and that one could recoil less.

 

[kostyanj]

What are you talking about? I'm talking about recoil which has nothing to do with pressure. You can have two loads using identical bullet weights, one generating more pressure than the other, and that one could recoil less.

I'm trying to convey to you that changing the charge OR bullet weight will affect recoil. Recoil is a force. Force=mass x acceleration
The acceleration comes from the pressure formed behind the projectile by burning powder.

Please explain to me how a load with identical weight as another but higher pressure will recoil less???

I'll be waiting...

 

[918v]

If you load a 125gr bullet to 40,000 PSI using Clays, it will have less recoil than if you load the same bullet to 40,000 PSI using HS-6. The reason is velocity. The HS-6 load will generate more velocity at that pressure level. You seem to think that pressure causes velocity. It doesn't. Energy causes velocity.

 

[kostyanj]

If you load a 125gr bullet to 40,000 PSI using Clays, it will have less recoil than if you load the same bullet to 40,000 PSI using HS-6. The reason is velocity. The HS-6 load will generate more velocity at that pressure level. You seem to think that pressure causes velocity. It doesn't. Energy causes velocity.

You're wrong and when I get home I'll post a few sources to disprove you. Just because a powder is slower burning does not mean the bullet is going slower or faster. 40kpsi is 40kpsi regardless of powder used. The pressure of the gasses compressed in the chamber accelerates the bullet. Those compressed gasses will have the exact same reaction at the same pressure regardless of powder.

 

[mahansm]

Kostyanj,

I beg to differ. You are looking at the peak pressure only, which does not tell the full story. To a close approximation, the energy of the projectile is the integral of the area under the pressure *curve*, which is shaped differently for different powders.

A fast powder will have a quick rise to peak pressure, and also a quick drop off, where a larger charge of a slower powder will build pressure more slowly, with a slower drop off. The slower powder may well impart more energy with a lower peak pressure.

We're also looking at recoil impulse, which is composed of the momentum of the projectile and the momentum of the propellant gases. More powder burned means more gas expelled from the barrel, and greater recoil impulse.

 

[kostyanj]

147s have the lowest recoil impulse of the factory loaded bullet weights. They are not the right choice for the SMG.

You need recoil, not pressure necessarily. One of the variables that affects recoil is the weight of the powder charge. A load using 7 grains of powder will recoil more than another that uses 5 even though both generate the same velocity and pressure. That leaves you with Power Pistol, Blue Dot, Herco, Accurate Arms #7, etc.

Don't be paranoid about dangerous pressure. The 9mm is a case capable of running 50,000 PSI and does in some loadings. Google "9mm Major" and go read about it at brianenos.com. It is basically a 9mm +P+++ that produces .357 Magnum ballistics with 115 and 125gr bullets. Amazingly guns hold up, cases hold up, nobody gets hurt, the world does not end, etc. Amazing!

In your case, you will not need to load it that hot. Based on what you wrote, you can get that SMG running with +P level loads. So in your research look for those loads driving 125gr bullets to 1200 FPS out of pistol barrels using slow burning powders.

My original post in this thread was made against this comment and it got derailed from there. I was just alluding to the fact that 147 can ONLY have the lowest recoil impulse IF the force (F=MA) is less than any other weight. This led into a discussion on acceleration (how pressure affects acceleration).

Then there's this quote:

"If you load a 125gr bullet to 40,000 PSI using Clays, it will have less recoil than if you load the same bullet to 40,000 PSI using HS-6. The reason is velocity. The HS-6 load will generate more velocity at that pressure level. You seem to think that pressure causes velocity. It doesn't. Energy causes velocity."

Velocity is Acceleration in this case but what is energy? We'd be using the pressure of the gasses in the chamber as a source of energy. In reality, it's the compression of the gasses that accelerate the bullet down the barrel. Acceleration = Pressure x Area / Mass If Pressure and Mass are held constant, then area and acceleration must change???

In reality what mahansm is saying is much closer to reality. I was oversimplifying it to drive a point home. The actual area under the pressure curve (the integral) is much more important. The reason being that the Area changes as the bullet moves. The pressure of the gasses is being released in all directions as the powder is ignited and as the bullet moves down the barrel, more surface area is exposed to the gasses.

918v, I'm not attacking you personally, but your first statement was full of inaccuracies. This gem particularly caught my attention:

"You need recoil, not pressure necessarily. One of the variables that affects recoil is the weight of the powder charge. A load using 7 grains of powder will recoil more than another that uses 5 even though both generate the same velocity and pressure. That leaves you with Power Pistol, Blue Dot, Herco, Accurate Arms #7, etc. "

You're go on to contradict yourself in later posts. The charge weight is completely irrelevant. The powder burn characteristics are far more important.


If I'm wrong in any of my analysis, I'd be glad to discuss it.

 

[918v]

My brain hurts.

 

[918v]

Slow burning powders require a heavier charge weight to reach the same pressure level as faster burning powders. Charge weight is a variable used in recoil calculator programs. I agree that the powder burn characteristics affect recoil more than charge weight, but slow burning powders have burn characteristics that do in fact increase recoil, mostly due to the additional velocity they generate.

 

[savanahsdad]

ok ok .... ,,,, ok boys , zip-em up and put away the rulers ! dose any one have any good loads for sub-guns other than the one I listed ? alsol this can happen with some gas op guns, my Ruger 44Carbine, and my Ruger DeerField (44mag) both need slow burning powder, W296 and 2400 both run those guns great, but bullseye or unique and other work fine in my wheel guns but wont run the auto loaders , my UZI like HS-6 , no need to overload to high PSI levels, you just need the right powder for some sub-guns and auto-loaders, I'd bet Win AutoComp would work great too, I have not tryed that yet , as I have found others that work ,