doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Low Pressure Question

To me 5000 PSI is the same regardless of what powder you use...

An SR-7625 load and a 700X load for example both producing equal pressrues are the same regardless of the pressure curve.

I shoot a damascus double. A fellow shooter insisted some powders produce less stress because the pressure is spread out over a longer portion of the barrel.

I think it's hogwash. Opinions please.

Thanks,
CraigF

Progressive powders do spread out the total pressure.

You peaked my interest - I have 7 booked 1.25 lead loads from BPI laying in front of me all with identical components except the powder - pressures range for 7500 psi with 800X to 10,000 psi with Unique and 10,500 with WSF. IMO any two 10,000 psi loads place indentical stress on the firearm. If the pressure curve was significantly differnt the slower powder (providing same components) would show a lower pressure. Just out of curiosity what is your pressure goal for the Damascus barrels? Just my thoughts.

Husky:
Not to be a nudge... but the word is "piqued."

Sorry for the public schools...

Geez, just when you think you know some douchebag, he shows you he can masturbate mentally, too.

That's "too", as in addition to his normal form.

Will the wonders never cease, and, desist?

We can hope, I guess.

Best,
Ted

"Normally" if you use powders having different burn rates with the same amount of shot to the same velocity you will get lower pressure with the slower powder. If you load them to the same pressure you would normally have a higher velocity with the slower powder. Although it will only be a slight amount the slower powder would also shift the point of max pressure a bit down the bbl. "Peak" pressure is normally measured at 1" from the breech to insure the max is always recorded. Even if the shift is only 1/16" the bbl wall is now a bit thinner.
By careful choice of powders you could load 1�oz of shot to 1300 fps & 1oz to 1200fps & have the same identical "Peak" pressure. If you think the heavier load doesn't put more stress on the gun, then you have a total failure to grasp internal ballistics.

"An SR-7625 load and a 700X load for example both producing equal pressrues are the same regardless of the pressure curve."

That's just imbecility.

'Peak' pressure is just that, peak chamber pressure.

The work done is contained under the pressure curve.

That's why there's a curve.

Shotgunjones-

But will it make a difference in a gun proofed for 850BAR?

I keep pressures low, 50% or less of proof pressure 5000-6000 PSI.

A chart showing 4 pressure curves all run with an identical 1�oz load to a 3 dram equivalent velocity has been posted here numerous times. This was run by DuPont back in the 1920's as I recall. Pressure curves are shown out to 10" from breech. Of note is the two points of maximum spread between the curves is first at the peak point inside the chamber, about 1�" from breech. The curves all then cross & switch positions about at the end of the chamber. The 2nd point of max spread between them then occurs at from about 4-6" from breech. Now pressure is considerably lower at this point, "BUT" bbl walls are also considerably thinner here as well.
My personal take on older guns is to restrict the amount of shot used as well as its velocity to just what is actually needed. I then try to use the fastest powder that will keep pressure within a 7K-8K range & figure I am doing the gun the best favor by keeping as much of the pressure as possible within the chamber where its walls are thickest. Also I don't generally have to worry about Cold Weather Squibs this way.

It takes the same energy to accelerate shot weight 'x' to velocity 'y' no matter the peak pressure involved.

It's just fizziks.

The pressure curve tells you where in the barrel the work is done.

The question is, as Miller points out, where would you like your 'stress'?

As far as does it make a difference... that's a question you have to answer for yourself. It's your gun and your eyeballs behind it.