.30-30-vs-.357 Ballistics Question

[slimster]

I know there are a great many people on this forum with a lot more smarts than me about these things, so I hope ya'll can help me figure this out. A top load in a .357 (carbine) will use 16-18 grains of a powder to realize 2000+ fps with a 158 grain jacketed bullet (2150+ with Buffalo Bore's factory loads in an 18.5 in. barrel according to them.) How come a .30-30 top load using 30-35 or so grains of a powder produces about the same or very little more velocity with a 150 grain jacketed bullet? Not trying to split hairs or anything here, it just seems that with a powder volume of nearly twice as much, there ought to be much more velocity difference than just a hundred or so fps. Thanks guys.

[Terry Murbach]

THE MAIN DIFFERENCE IS IN THE BORE SIZE. THE 357 BULLET HAS NEARLY TWICE THE AREA FOR POWDER GASES TO PUSH UPON TO DRIVE THE BULLET DOWN THE BORE. THE SMALLER BULLET ALSO HAS A LOT MORE BEARING SURFACE TO BE ENGRAVED BY THE RIFLING WHICH RAISES PRESSURES NICELY. THE 357 USES PROPELLENTS OF MUCH FASTER BURN RATE THAN THE 30-30 RIFLE CARTRIDGE AS THE STRAIGHT WALLED CASE NEEDS THEM TO COME UP TO PEAK PRESSURES RAPIDLY IN COMPARISON TO THE BOTTLENECKED RIFLE CARTRIDGE.
ONCE YOU'VE DIGESTED THAT THINK OF THIS : THE SMALLER 30 CALIBER BULLET HAS AT LEAST TWICE THE EFFECTIVE RANGE OF THE FATTER SQUAT 35 CALIBER BULLET.
THERE IS A LOT MORE TO ENTER INTO THIS BUT I AM NOT IN THE BOOK WRITING MOOD THIS AFTERNOON.
AND THEN LOOK AT WHAT HAPPENS WHEN YOU SHOOT THOSE 35 CALIBER BULLETS FROM A RIFLE CARTRIDGE LIKE THE 35REM OR THE 356WIN. BIG DIFFERENCE !!!!
AND ONE OTHER THING : THE 357MAG PROPELLENTS ARE LONG GONE WHILE THE 30-30'S ARE STILL MAKING GAS AND STILL PUSHING ON THE BULLET.
DO NOT LOSE SIGHT OF THE FACT THAT THE 357MAG IN A LIGHT SHORT CARBINE IS ONE WHALE OF A CARTRIDGE FAR REMOVED FROM IT'S USE IN A 357 SIXGUN, AND ACTUALLY IS MORE POWERFUL THAN THE 44MAG IN A SIXGUN. THERE ARE NO FLYS IN THE 357MAG'S PERFORMANCE FROM A CARBINE OR RIFLE; NONE !!!

[slimster]

Thank you for your help Mr. Murbach. The variables are mind boggling. Your short form answer has helped a lot, but makes me begin to realize just how much there is to learn about ballistics! Again, many thanks.

[polardaddy]

slimster,

I am right there with you.

[Doc Hudson]

I'm not trying to steal any of Terry's thunder, but have you read Paco's article on the .357 magnum in rifles?

If not you should, it will add more info to what Terry statated.

http://leverguns.com/articles/paco/357_ ... rature.htm