The 358 Winchester

[BBCT]

How is it possible to fire a heavier bullet, with lower pressure, at a higher speed?

As a rule of thumb, when all other things are equal, the bullet with the greater cross sectional area can be launched at a higher velocity.

Janfred gave the maths, but to use an example we can all relate to, a 150gr bullet from a .30-06 can be launched at a higher muzzle velocity than a 150gr bulet from a .270 when all other things are equal. We all know that the .30-06 and .270 cases are for all practical purposes the same other than neck diameter, we can even use the same powder (S365) in both. The .30-06 bullet will however lose velocity faster than the .270 due to greater frontal area hence less sectional density for the same bullet weight.

The fact that the bullet can be launched at higher velocity as well as the fact that it loses velocity faster are both attributable to the cross sectional area of the bullet via the formula Force = Pressure x Area, which tells us that for the same pressure, a greater area will give us more force.

Now that I read back on this, I'm not so sure that I've explained it as well as it can be explained, but hopefully you'll get the idea............

[Ds J]

Die Brits maak my moeg

n Langer, dunner koeël trek beter deur die lug as n dikker, korter koeël van dieselfde gewig.

En n dikker, korter koeël word makliker gedryf omdat die dryfgas meer vatplek aan die korter koeël het.

Dus behoort n 358 beter weg te trek, en die 308 behoort beter oor n langer afstand te trek as die koeëls se gewigte ooreenstem.

[janfred]

My bad. Teach me to read what is actually there...

I was under the impression that there is no reliable way to convert between CUP and PSI.

Whatever the actual allowable maximum pressure, the calculations show that bore size trumps pressure. At least for the initial acceleration. Next would be available case capacity that would govern how long the pressure is maintained.

[Treeman]

How is it possible to fire a heavier bullet, with lower pressure, at a higher speed?

As a rule of thumb, when all other things are equal, the bullet with the greater cross sectional area can be launched at a higher velocity.

Janfred gave the maths, but to use an example we can all relate to, a 150gr bullet from a .30-06 can be launched at a higher muzzle velocity than a 150gr bulet from a .270 when all other things are equal. We all know that the .30-06 and .270 cases are for all practical purposes the same other than neck diameter, we can even use the same powder (S365) in both. The .30-06 bullet will however lose velocity faster than the .270 due to greater frontal area hence less sectional density for the same bullet weight.

The fact that the bullet can be launched at higher velocity as well as the fact that it loses velocity faster are both attributable to the cross sectional area of the bullet via the formula Force = Pressure x Area, which tells us that for the same pressure, a greater area will give us more force.

Now that I read back on this, I'm not so sure that I've explained it as well as it can be explained, but hopefully you'll get the idea............

*************************
Yes, it is put across well enough.

[BBCT]

Die Brits maak my moeg

n Langer, dunner koeël trek beter deur die lug as n dikker, korter koeël van dieselfde gewig.

En n dikker, korter koeël word makliker gedryf omdat die dryfgas meer vatplek aan die korter koeël het.

Dus behoort n 358 beter weg te trek, en die 308 behoort beter oor n langer afstand te trek as die koeëls se gewigte ooreenstem.

Jy't dit korter en beterererder beskryf as wat ek kon.  ;-)