Why is it so?

[Blr243]

Reading adi handloaders tables we see a certain load might give 3700 FPS and the pressure is listed beside it. Generally it makes sense that another load offering 3750 FPS should have A higher pressure than the first load. But sometimes the opposite is the case. One would think that every time the pressure is higher, the velocity should be too ..... I have always, for decades in fact wondered about this ...can someone shed some light please ?

[Ziege]

has to do with burn rate vs available space in the case vs bullet weight/expansion of area gas occupies etc... theres a lot to it.

[Blr243]

So maybe a higher initial pressure, but a pressure that drops off quicker, and therefore does not push the bullet as fast ? Sounds like a deep , complex situation

[Ziege]

well each situation is entirely dependent on the projectile, powder and charge and case... even primer and freebore and all that... so yeah

[bladeracer]

Scientific phenomenon called "just because"

[animalpest]

Loading say, 2208 will give velocity of 3700 fps. The case is only filled to 90% capacity.
But if you load with a slower powder, 2209, velocity may be slightly higher with a near 100% fill of the case.
The 2209 burns and pushes the bullet for a longer period of time with the same peak pressure.

[Larry]

The bearing surface of the bullet is an important spec. The more surface area the higher the friction in the barrel which slows the bullet down.

[Blr243]

Gradually. I’m getting it .....

[marksman]

Haaa Haaaaa Blr you are starting to see that oils aint oils
Why is it so, hmmmm

this is well and truly because of COAL and lead
but my friend l could babble on and take the credit all day to give you an answer to "Why is it so"
the explanation would be better from an expert like Bryan Litz who can explain it much better than l could, enjoy
https://bergerbullets.com/effects-of-ca ... to-part-1/

this is something everyone should know about before having a custom chamber cut

l forgot to add fark sammi

[Blr243]

Thanks for the link marksman. And I also need to know from u lot which paddock I should be hunting because my second stint tonight will be my last chance and I just can’t seem to get it right

[marksman]

l would be hitting the paddock that gets the first shade,
sitting back aways waiting for the beasts to come out of the bush then shoot the farkers in the head and take them home for salami if you have a good recipe

[LawrenceA]

Depending what you mean by another load it may well be due to the pressure curve created by the burning powder.
If you think of it like a car accelerating down a 20km road (the barrel).
If the car accelerates at 20km/hr per second for 3 seconds it is going 60km/h for a given amount of pressure on the motor.
If the same car accelerates at 15km/h per second for 4 seconds it is doing the same speed but did so at less pressure.
So a fast burning powder is a quick push and a slow burning powder is a slower push over a longer period.

[Bugman]

As the late Professor Julius Sumner Miller said, "why is it so?.........buggered if I know"