Cartridge efficiency
- Thread starter Grimstod
- Start date
Basically less for more. Meaning if you can design a cartridge that uses way less powder and you get more speed for that charge weight and more efficient burn.In my opinion if you could get a cartridge to burn all the powder in the case versus burning all the way down the barrel you would really have something there.Look at the 6mm Remington versus the 6mm BR and you will get the picture or the 6ppc,short powder column ,fast complete burn makes good velocity. How about some of the weatherby cases using alot of powder to barely beat out a competitor in a similar cartridge like the .224 weatherby versus the 22 ppc or 22 br using less powder and almost shooting similar velocity's as the weatherby.I am not slamming weatherby but if you can design out all the powder pigs your supply of powder will last you longer.Meaning rounds per pound.Take for instance the .223 Remington versus a standard plain jane 22-250. With some of the newer powders the .223 will be in the same neighborhood as the 22-250 when you consider the average load is 24.0 grains in the .223 and the 22-250 uses 35 on up to get that little more. Barrel wear is common on these overbore cartridges.I hope my rambling has given you the idea. I am sure someone will doubt some of what I have said but there are alot of powder pigs in use and I own some too.
CatShooter
Grimstod said:I sure Hope I am not waking up a wave of controversy here. :
Anyway what makes a cartridge more efficient. I see the term a lot when books talk about the various cartridges and their different attributes.
To be more efficient, you would need a case design/shape with the same volume, that used the same amount of powder, at the same pressure, and delivered more energy.
So far, there are none.
Comparing a small case to a large case does not apply for this comparison. That would be like comparing a VW to a Chrysler.
savagedasher
Banned
CatShooter said:6.5 Jody it has a curved shoulder.Grimstod said:I sure Hope I am not waking up a wave of controversy here. :
Anyway what makes a cartridge more efficient. I see the term a lot when books talk about the various cartridges and their different attributes.
To be more efficient, you would need a case design/shape with the same volume, that used the same amount of powder, at the same pressure, and delivered more energy.
So far, there are none.
Comparing a small case to a large case does not apply for this comparison. That would be like comparing a VW to a Chrysler.
As jonbearman said, getting more out for less in is what makes for an efficient cartridge. Example:
243 WIN vs 6 BRX
243 WIN, 42.5 grains of H4831sc = 3000 fps and about 10-12 reloads with standard brass
6 BRX, 33 grains Varget = 3000 fps and about 20-30 reloads with 6BR brass.
That's more efficient! However, one will feed from a magazine and one will not....now the efficiency equation has been reversed. ;D
243 WIN vs 6 BRX
243 WIN, 42.5 grains of H4831sc = 3000 fps and about 10-12 reloads with standard brass
6 BRX, 33 grains Varget = 3000 fps and about 20-30 reloads with 6BR brass.
That's more efficient! However, one will feed from a magazine and one will not....now the efficiency equation has been reversed. ;D
I'll throw this out there for discussion....The easiest way to increase a cartridges efficiency is to neck it up.
In terms of mechanical / thermal efficiency with the firearm as a heat engine, it's a relatively straightforward matter of the interrelationship of case capacity / charge weight, calibre, and maximum allowed chamber pressure with the emphasis on the first two factors.
Small cartridges are always more efficient in these terms than larger models of the same calibre. The easiest way of comparing designs is to take the muzzle energy in ft/lbs and divide that by the charge weight to get an energy per grain of powder figure. On that basis, the .22 Short and Long Rifle are likely the most efficient models in general use with around 1.5gn or powder in a standard velocity LR producing 1,050 fps with a 40gn bullet, or 98 ft/lb = ~ 65 ft/b per gn. Increase the cartridge to .223 Rem size, the same bullet/bore dia give or take a thou' and it takes maybe 25gn powder to get a 55gn bullet to 3,250 fps (1,290 ft/lb) the equivalent efficiency figure being 51 ft/lb per grain weight of propellant charge, a 22% efficiency reduction compared to the rimfire despite running at much higher chamber pressures.
From .223 Rem upwards in case capacity and charge weight, things can only get worse as we move into over bore-capacity territory, the .223WSSM using 45-50gn to get the additional 500 fps over the 223 with a 55gn bullet. 45.7gn IMR-4350 gives a 55gn bullet 3,738 fps to pick a load at random from the Berger Reloading Manual, that's 37 ft/lb per grain of propellant, a 43% efficiency reduction on .22LR and 27% down on the .223 Rem figure.
That could be improved by increasing barrel length as the more powder being burned, the longer the barrel needed to obtain the optimum velocity. With a standard velocity .22LR, 12-15 inches of barrel are all that's needed while the .223WSSM would need an impractically long barrel to get there, maybe 10 ft or so.
Keep the case size, pressure and powder charge weight constant while varying bore size changes the thermal efficiency increasing the bore diameter normally increasing its value. So, compare the .243WSSM to its .223 smaller sibling and a 90gn bullet exits the muzzle at 3,137 fps, 1,967 ft/lb ME, using 44.0gn IMR-4350 again quoting the Berger manual and both using 24-inch test barrels. That's 44.7 ft/lb per grain of powder.
If you take the .308 Win cartridge 'family' sharing the same case and using not dissimilar amounts of powder, the least efficient is the .243 Win and the most .338 Federal and .358 Win. So, why do far more people use the 6mm model than the large bores? Because there's more to shooting than crude ME values, the smaller calibres being superior in external ballistics for anybody other than short-range brush hunters. You don't see many .338 Fed rifles in 1,000 yard F-Class matches either, fine cartridge though it is, and with some superb long-range match bullets available too.
What happens to the 'lost' energy in the larger cased cartridges? More Joules of propellant energy are used in producing noise, muzzle blast, recoil, and most of all wasted heat.
The other issue that exercises shooters' minds and makes for many a range-house discussion is of course, case shape with many arguing that short, fat PPC type designs with minimal body taper and sharp-angle shoulders are inherently 'more efficient' than those that are long, skinny and heavily tapered. For those inclined to believe in this argument, compare the .300 WSM to the ancient .300 H&H Magnum a design that lacks a single redeeming feature in this lexicon. As luck would have it, they have near identical case capacities and are both rated at 65,000 psi PMax, and of course are identical calibre and shoot the same bullets. Look at a bunch of handloading manuals or run loads through QuickLOAD and you won't see a penny's worth of difference in the MVs they produce for any given bullet over the same powder type if the barrel length is also the same.
That's not to say that there are no advantages in having a short powder column in a fat case with sharp shoulders to do with ignition consistency and burn pattern, ability to use a short action etc, but increased efficiency doesn't figure except in one relatively marginal way. The .300 WSM has around an extra half inch of 'effective barrel length' in any overall length as its short case sees the throat and leade that amount closer to the bolt-face.
Small cartridges are always more efficient in these terms than larger models of the same calibre. The easiest way of comparing designs is to take the muzzle energy in ft/lbs and divide that by the charge weight to get an energy per grain of powder figure. On that basis, the .22 Short and Long Rifle are likely the most efficient models in general use with around 1.5gn or powder in a standard velocity LR producing 1,050 fps with a 40gn bullet, or 98 ft/lb = ~ 65 ft/b per gn. Increase the cartridge to .223 Rem size, the same bullet/bore dia give or take a thou' and it takes maybe 25gn powder to get a 55gn bullet to 3,250 fps (1,290 ft/lb) the equivalent efficiency figure being 51 ft/lb per grain weight of propellant charge, a 22% efficiency reduction compared to the rimfire despite running at much higher chamber pressures.
From .223 Rem upwards in case capacity and charge weight, things can only get worse as we move into over bore-capacity territory, the .223WSSM using 45-50gn to get the additional 500 fps over the 223 with a 55gn bullet. 45.7gn IMR-4350 gives a 55gn bullet 3,738 fps to pick a load at random from the Berger Reloading Manual, that's 37 ft/lb per grain of propellant, a 43% efficiency reduction on .22LR and 27% down on the .223 Rem figure.
That could be improved by increasing barrel length as the more powder being burned, the longer the barrel needed to obtain the optimum velocity. With a standard velocity .22LR, 12-15 inches of barrel are all that's needed while the .223WSSM would need an impractically long barrel to get there, maybe 10 ft or so.
Keep the case size, pressure and powder charge weight constant while varying bore size changes the thermal efficiency increasing the bore diameter normally increasing its value. So, compare the .243WSSM to its .223 smaller sibling and a 90gn bullet exits the muzzle at 3,137 fps, 1,967 ft/lb ME, using 44.0gn IMR-4350 again quoting the Berger manual and both using 24-inch test barrels. That's 44.7 ft/lb per grain of powder.
If you take the .308 Win cartridge 'family' sharing the same case and using not dissimilar amounts of powder, the least efficient is the .243 Win and the most .338 Federal and .358 Win. So, why do far more people use the 6mm model than the large bores? Because there's more to shooting than crude ME values, the smaller calibres being superior in external ballistics for anybody other than short-range brush hunters. You don't see many .338 Fed rifles in 1,000 yard F-Class matches either, fine cartridge though it is, and with some superb long-range match bullets available too.
What happens to the 'lost' energy in the larger cased cartridges? More Joules of propellant energy are used in producing noise, muzzle blast, recoil, and most of all wasted heat.
The other issue that exercises shooters' minds and makes for many a range-house discussion is of course, case shape with many arguing that short, fat PPC type designs with minimal body taper and sharp-angle shoulders are inherently 'more efficient' than those that are long, skinny and heavily tapered. For those inclined to believe in this argument, compare the .300 WSM to the ancient .300 H&H Magnum a design that lacks a single redeeming feature in this lexicon. As luck would have it, they have near identical case capacities and are both rated at 65,000 psi PMax, and of course are identical calibre and shoot the same bullets. Look at a bunch of handloading manuals or run loads through QuickLOAD and you won't see a penny's worth of difference in the MVs they produce for any given bullet over the same powder type if the barrel length is also the same.
That's not to say that there are no advantages in having a short powder column in a fat case with sharp shoulders to do with ignition consistency and burn pattern, ability to use a short action etc, but increased efficiency doesn't figure except in one relatively marginal way. The .300 WSM has around an extra half inch of 'effective barrel length' in any overall length as its short case sees the throat and leade that amount closer to the bolt-face.
What I didn't see mentioned in Laurie's post is that with a small case/ bore ratio, the cartridges will utilize faster burning powders, doing the same work in less time and space than their slower cousins. This reduces muzzle pressures and less muzzle blast, creating less recoil and potentially better accuracy. This IMO, is where the more efficient cases see the biggest improvement over their big brothers.
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