Pressure Question

KnotRight

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Using the same gun and same bullet to reach a stated velocity, would the pressure be the same for different powders. I am not asking about the amount of powder.

Where I am going with this is a Trapdoor 45-70 using a 405 grn bullet trying to get 1350 ft/sec. Using say 25 grns of one powder and 30 of another whould the pressure be the same. Now I know the powder has to be for the 45-70.
 
, would the pressure be the same for different powders. .

Not necessarily.

You certainly would not want to try a new powder with a very different burning rate for which there are no data available and keep putting in powder until you reached the velocity that you get with another powder. You may get a pressure spike that is unacceptable.
 
rdinatal and Charlie I agree with your comments.

The trapdoor best velocity should be around 1350 ft/sec. If a powder starts it load at 1350 but does not show "Trapdoor" loads would you use it? I want a backup powder for H4198. I have been using Shooters World Buffalo Rifle in the Marlin and Ruger 1 and a little concern to use it in thr Trapdoor.
 
rdinatal and Charlie I agree with your comments.

The trapdoor best velocity should be around 1350 ft/sec. If a powder starts it load at 1350 but does not show "Trapdoor" loads would you use it? I want a backup powder for H4198. I have been using Shooters World Buffalo Rifle in the Marlin and Ruger 1 and a little concern to use it in thr Trapdoor.
If the Trapdoor is not listed, I would not use it.
To many other powders that are safe for Trapdoors out there to risk the gun or myself/yourself.
 
Probably not. If Powder B is close on the burn rate chart to Powder A it might, in theory, result in a similar peak pressure. But there are so many other variables in play... I'll stand over there and watch while you test that.

FWIW I will go off book when the books don't cover my use at all, but only then. If there's a published alternative I'd go with it.
 
Hodgon published data for trapdoor actions and i think they post pressures from their testing devices.
 
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The velocity is all about the total "area under the curve". Think of it as a plot of the pressure at various points along the barrel. The pressure is not constant, it will peak very soon, in some cases before the bullet has fully left the brass, but certainly within the first inch or so of travel. Then it drops, and continues to drop, as the bullet travels down the barrel, but the pressure is still high enough to continue accelerating the bullet all the way to the end.

Different powders have different burn rates, which affects how soon the pressure peaks, and how fast it drops off. A very fast burning powder will peak quickly and then drop off quickly, so even if it reaches the same PEAK pressure as a slower burning powder, it will result in less velocity due to the area under the (pressure) curve.

Burn rates are just relative, and will vary with the application. Gather some burn rate charts from various sources and you will notice that the charts are different, with some powders moving up or down depending on which chart you look at.

Having said all that, it you are specifically looking for trap-door safe loads, only look at data specifically listed that way.
 
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