Most efficient cartridge?

[enfieldspares]

I always used to look at the .455 Webley in comparison to, say, the .38 Special and .357 Magnum.

The .455 Webley cartridge as it developed got shorter as the old blackpowder was superceded by smokeless powders particularly cordite. Thus the .455 Mk I cartridge is longer than the .455 Mk II cartridge.

The .38 Special or more correctly .38 Smith & Wesson Special however was a blackpowder design which the result of lengthening the .38 Long Colt to get more blackpowder inside it to get a higher velocity. All well and good. So the first .38 Special cartridges used blackpowder.

Except..

When modern smokeless powders soon came along rather than shorten the cartridge as the British had done with the .455 Webley it was kept the same length. Then along comes the .357 Magnum which for safety to stop its use in .38 Special revolvers had the case made even longer!

So most of the American classic revolver cartridges are actually inefficient or more correctly unnecessarily long for the modern powders that exist today.

To see what the then modern powders the Germans were using could achieve pre-WWI one only has to look at the velocity that a German 9mm Parabellum cartridge produces in but 19mm case length compared to the velocity produced by the old blackpowder .38 S & W cartridge of almost identical case length.

 

[Foxyboy43]

222

God’s very own….

 

[Bavarianbrit]

RIP Mike Walker.

 

[Greenmist]

Cartridge design wise, shorter and fatter appears to be more efficient than the traditional longer cases

 

[Laurie]

Cartridge design wise, shorter and fatter appears to be more efficient than the traditional longer cases

More efficient (consistent) in the way the powder column burns, yes. More efficient in producing a greater amount of energy (ME) for the same energy input from the powder charge, no. (This assumes other factors are common to both cartridge types - case-capacity/bore-size ratio; powder charge and weight; peak pressure; barrel length etc.) Compare the powder charges used and MVs produced by the 300 WSM (which meets all the criteria for a modern 'efficient' design) and the antediluvian 300 H&H Magnum (which has everything 'wrong' in design terms). The pair have very similar case capacities and are both rated at 65,000 psi PMax. There is very little difference in the size of the bang for the buck between the two. Which would I use for a long-range precision rifle? The WSM any day as the short case with little taper allied to a steep shoulder angle gives very consistent ignition and charge burn, hence low pressure and MV spreads and tends towards higher precision results. (The ancient H&H Magnum is capable of very high degrees of precision though and was used as a long-range match cartridge for many decades.)

There are likely other (mechanical) factors too. Creighton Audette showed experimentally how varying wall thickness around the case circumference increased group size caused by the thin-walled side of the case stretching more in the chamber under pressure and tilting the case-head away from true alignment with the bolt-face - the so-called 'banana case'. He hypothesized that short, fat cases distort less than long thin ones when such conditions apply. (It might also be that case manufacturers can make short cases with fewer wall-thickness variations than for long steeply tapered ones.) Shallow shoulder angles allied to short necks (eg 243 Winchester) are reckoned to wear barrels out quickly through the resulting 'torch effect' or 'turbulence point', a ball of super-hot gas / erosive part-burned powder kernels being pushed outside of the case-neck. The David Tubb designed 6XC takes a similar case, increases the shoulder to a 30-deg angle and has a longer neck on top which (allegedly) keeps the nasty stuff inside the neck and away from the throat/leade area of the barrel. (This feature applies to most modern designs such as the Creedmoors, but many much older ones such as the 6.5X55mm are as good if not better in this respect.) Much of this is theory/hypothesis and very difficult to prove one way of the other, although users of the 6mm Rem with its sharper shoulder + longer neck claimed for many years that their cartridge gave better barrel life than the 243 Win despite running slightly more powder allied to higher higher pressures and therefore giving a bit more MV to the same bullets.

 

[6.5-06 TIKKA]

The .22 and 6mm PPC must be included too here...

 

[cjm1066]

The 300 WSM is designed to burn powder more efficiently, the 300 H&H will almost certainly feed better in a bolt action rifle.

Horses for courses as they say both launch a bullet at similar speed, one is more likely to give you a second shot.

 

[the prowler]

How efficient is 20vartarg?

 

[finnbear270]

How efficient is 20vartarg?

You already know!

 

[the prowler]

You already know!

 

[finnbear270]

Laurie, not sure if I grasped the formulae / math, is 36 grains of powder 3000fps @ muzzle / 2400 ft/lbs looking like 83 and 66? .25-06Rem.

 

[Buggadifino]

In the search for efficiency you could spend a great deal of time and effort in chasing small returns.

In general cartridges will be about 30% efficient. 60% is taken up moving the gas column and 10% is lost to heat and noise leaving 30% of your energy to move the bullet.

 

[Bavarianbrit]

A single cylinder heat engine.