CARTRIDGE EFFICIENCY

AVID HANDLOADERS sometimes talk about cartridge "efficiency," but few try to define that efficiency.  During one discussion a young handloader described the 7mm Remington Ultra Magnum as efficient, because it achieves more velocity from 7mm bullets than any other factory round.  Was he wrong?  Other handloaders might say so, but few of them step forward with their own definition - and if efficiency means achieving a certain velocity, then the 7mm RUM is by definition the most efficient 7mm rifle cartridge.

There are other contradictions.  Take a look at shotshells.  On one hand, shotshells have a very high powder-to-energy ratio.  A typical 1-1/4 ounce 12-gauge load might use 20 grains of powder to produce 2000 foot-pounds of muzzle energy, or 100 foot-pounds per grain of powder.  A 7mm RUM might use 90 grains of powder to produce 3600 foot-pounds, or 40 foot-pounds of energy per grain of powder.  So if we define efficiency as grains of powder used per unit of energy, then the 12-gauge is 2-1/2 times as efficient as the 7mm RUM.

On the other hand, many experienced pheasant hunters think hitting a bird with five pellets is about right.  Fewer hits can result in a long chase by the Labrador; more hits mean too many holes in the breast meat.  A 1-1/4 ounce load of #6 shots contains around 280 pellets, so if five hit a pheasant 275 pellets miss, a "hit ratio" of under 2%.  Any way you look at it that's inefficient - but it's still a lot more efficient than shooting all day at flying pheasants with a 7mm RUM.  Most likely you won't hit any pheasants, and if you do there won't be much breast meat left, not unless you get really lucky and hit the bird in the head.

So the purpose of any cartridge also has something to do with how we define efficiency, even if we limit the discussion to rifle rounds and powder-per-foot-pounds.  The most efficient rifle cartridge on the market is the .22 Long Rifle.  A high-velocity load develops 150 foot-pounds of muzzle energy with around 1.5 grains of powder.  The powder ratio exactly matches the 1-1/4 ounce 12-gauge load, producing just about 100 foot-pounds per grain of powder.  But most of us wouldn't choose the .22 Long Rifle for hunting deer.

Instead we might choose the .30-30 Winchester, and a lot of us have.  The .30-30 produces about 1800 foot-pounds of muzzle energy with 30 grains of powder, 60 foot-pounds per grain of powder.  This is a little better than the 7mm RUM's 40 foot-pounds-per-grain, but not much.  The big difference is in recoil.  A 7mm RUM weighing eight pounds will produce over 35 foot-pounds of energy with a typical 140-grain load, while an 8-pound .30-30 will produce under 10 foot-pounds of recoil energy with 170-grain ammo.

Now there's no doubt that the 7mm RUM will do a better job on deer at 500 yards than will a .30-30.  But 95% of all deer are killed at under 200 yards, even mule deer, and a .30-30 is plenty for deer out to 200 yards.  In fact the average hunter would probably do better with the .30-30, because he'd put the bullet in the right place instead of flinching and missing, or hitting the deer in the guts.  So aside from the powder-to-energy ratio, the .30-30 is a more efficient deer cartridge than the 7mm RUM at normal ranges.  At 500 yards the 7mm is more efficient, but how many of us shoot deer at 500 yards?

Recoil is a big part of the efficiency equation, and ignoring it is foolish.  My wife Eileen, for instance, really likes to shoot shotguns and hunt birds.  But she gets a recoil headache with anything much over the standard 28-gauge load of 3/4 of an ounce of shot at 1200 fps or so.  She can push that a little with 20-gauge loads using an ounce of shot, if the shots are spaced out over a day, but anything heavier practically guarantees a headache after a few rounds.  So she mostly uses a 28-gauge and, not so oddly, does quite well with the 28, even on birds as big as pheasants and sage grouse.

Of course, we can also up the efficiency of the .30-30 by making the bullet smaller and faster.  The result is basically the .250-3000 Savage.  The .250 appeared 18 years after the .30-30 and only uses a little more powder, but it's miles ahead in another kind of efficiency: putting a lighter, faster bullet in the right place beyond 200 yards.  This is because the .250 uses a pointed ("spitzer") bullet at higher velocity than the .30-30.  Even with the extra velocity, the .250 recoils even less than the .30-30.  Double efficiency!

Trouble is, how many .250-3000's do we find anymore?  There are quite a few old Savage 99's chambered for it, but not many other rifles, and Savage 99's have increased in value since they ceased being made in the 1990's.  In fact, as one guy noted to me at a recent gun show, "I didn't know I was a millionaire until I checked out the price tags on the Savage 99's!"  Of course, "asking" price isn't "getting" price, but today the average Savage 99 .250 costs a lot more than the average Savage bolt-action .243.

The .243 Winchester is, of course, the modern version of the .250-3000.  It isn't quite as efficient in terms of powder-to-energy, but these days buying a .243 (whether new or used) is a lot more dollar-efficient than buying the average .250 Savage.  And a .243 still kicks about like a .30-30.

Extra recoil is one price we pay for using cartridges with less efficient powder-to-energy ratios.  By their very definition such cartridges use more powder in smaller bores.  This means that the gas produced by the powder adds even more "rocket effect" to recoil.

Never heard of rocket effect?  Recoil is the result of one of Newton's basic laws: Every action has an equal and opposite reaction.  This means that when stuff goes flying out the muzzle of any firearm, the firearm tends to head the opposite way.  One part of the stuff is the bullet (or shot charge), but the other part is powder gas.  In a cartridge like a .22 Long Rifle or a 12-gauge shotgun, almost all of the recoil is due to the projectile leaving the muzzle, but in a 7mm RUM a huge part of recoil is the large amount of hot gas leaving the muzzle at high pressure.

This means that in large-capacity, small-bore "magnum" cartridges, recoil becomes increasingly out of whack with the actual energy produced by the bullet.  Want proof?  As noted already, a 140-grain load from a 7mm RUM produces over 3500 foot-pounds of muzzle energy AND over 35 foot-pounds of recoil in an 8-pound rifle.

The little 7mm-08 Remington round produces around 2600 foot-pounds of muzzle energy with a warm but reasonable 140-grain handload, but only around 15 foot-pounds of recoil in an 8-pound rifle.  This means the 7mm-08's muzzle energy is 72% of the 7mm RUM's, while the 7mm-08's recoil is only around 40% of the RUM's.  The difference in percentages is purely due to hot gas, which does nothing for "killing power" at any range.

The other price paid for using more powder in the same bore-size is barrel life.  Now, most of us won't ever be lucky enough to burn out the barrel of the typical deer rifle - unless, of course, we spend each weekend practice-shooting 100 rounds or more with the same rifle.  Some deer hunters do that, and like screwing in a new barrel every year.

Most hunters, however, are much more likely to burn out a barrel shooting varmints like prairie dogs, partly because when PD's are abundant (and they often are) we keep shooting even when the barrel gets hot.  Hot barrels burn out quicker.  I have seen .22-250's burned out during a 3-day prairie dog shoot, believe it or not.  By "burned out" I mean the barrel no longer made sub-inch, 5-shot groups at 100 yards, which means it wouldn't consistently hit a prairie dog at 300 yards.

At the other extreme, a buddy of mine recently (and finally) put a new barrel on his favorite .223 Remington.  He kept a fairly close round-count over the years and figured he'd put 20,000 rounds through the barrel before it quit shooting sub-inch 5-shot groups.  I've shot prairie dogs with him a number of times and believe me, he didn't baby that barrel.

It's also possible to watch the bullet hit through the scope of a heavy barrel .223 - but not with a .22-250, at least not unless the .22-250 weighs over 15 pounds.  While a .22-250 may allow us to occasionally hit a prairie dog way out there a little more often than when shooting a .223, the reality is that very few people can consistently hit prairie dogs at more than 350 yards anyway, especially in a typical high-plains wind.  All of which is why you'll find a lot more .223's than .22-250's in the hands of prairie dogs hunters.

So efficiency takes different forms, and a lot depends on the use the cartridge will be put to.  Sometimes a .243 is more efficient than a 7mm magnum, and sometimes it isn't.  The same applies to the 28-gauge and the 12-gauge.  The big thing is to honestly assess your shooting in terms of desired results, recoil tolerance and finances, and then make an informed choice.

But if you really, truly want an efficient rifle, buy a .22 rimfire. ...