What is the maximum barrle lenght for maximum velocity.

It depends on the Caliber

What is maximum velocity? Please define. Cheers! Ming

The velocity would contiune to increase with each additional inch, but after a certain point the rate of increase per inch would start to decline. Most cartridges lose about 15-30 fps per inch of barrel less than the test barrel for that cartridge. A barrel of 34" would be fast, but how practical?

Overkill,

With a good gunsmith nearly all is possible. I have already seen for a 9.3X62 a 32.5" barrel on an Oehler Model 33.

While I don't have "the answer" there are a couple factors

1: bullet drag aka, is it DOING anything better? I was determined by Ackley and others, that once you hit about X length, you really aren't adding anything becuase the exposive column has run it's course. It's cubic volume has exceeded the point where it's adding ANYTHING OF VALUE to the final vel of the round.
2: You can look it as an expression of bore/case capacity aka "being over bore". If you take, say, a .308 barrel, and make it, oh 48" long, i bet you could get the most out of a 30-378, but, in a 308 vs a 24" barrel , it wouldn't be anyting like as great. I ran this through quickload, and it basically hold out. You get MORE increase in vel with the LARGER bore to capacity, 24 vs 48" barrels
3: usability/human factors. a carbine (mod 7 or so) is about 40" oal, and the same thing, in a long barreled sendero is 46 5/8". and it "feels" much longer. So, usefulness in the field MIGHT play a factor in max length.
4: longer barrels, under a relevant range, can produce higer vel. Look at the 50 bmg, normally 30+ inches long. ours is 20".. and we loose TONS of energy (that might be the first time i've used that phrase correctly) for it being somewhat handy.

in a nutshell, I think useful barrel length is more determined by human factors than science. If it wasn't, all small bore "magnums" would have 28" tubes on them. I can't believe that 7 rem mags "normally" have a 24", and can be had at 22". Shesh, get a 7-08 for that length, and WOW, they are just about the same velocity. Even the malaligned 350 rem mag shines with a 24" tube.

jeffe

Past "X" length the powder is spent but bore friction is not, so any barrel longer than X will slow the muzzle velocity with any further increase in barrel length. However, this is well past any useful barrel length for a sporting firearm, whatever the caliber or expansion ratio. Somewhere I saw this documented by testing. The velocity will decline with each additional inch.

Overkill,

It is cartridge dependant. You can start with a very long barrel and check the temperature of the barrel. Where the barrel get cold you have exhausted your powder. This "cold line" is were you cut.

With most of the 416 Rigby based super mags up to 375 caliber the optimum barrel length seems to be around 30 inches.

Todd E

The cold line, would the friction also heat the barrel therefore it would be difficult to see at what point the powder was expended.

BER007 what velocity did the gentleman with the 32" barrelled 9.3x62 getting??

Optimum barrel length is really an interesting question and probably has no definitive answer although each cartridge will obviously posses a barrel length from which optimum velocity can be achieved. Unfortunately, in the real world this often comes at a point of minimal accuracy. There is always a trade off. In reality, for most cartridges velocity continues to increase about 30-50fps for each inch of barrel length till about 40 inches afterwhich it will decrease with increasing frictional forces.Unfortunately, a 40 inch tube has so many wierd vibrational nodes in it that accuracy is seldom obtained. The really big bores like the .50 BMG using the slowest possible powders need about 36-38 inches for max velocity while the .357 Mag in a rifle using fast pistol powders is done for by 16 inches. I'm sure this can all be calculated for each different cartridge barrel combination.-Rob