Is the .308 a Viable Long Range Cartridge?
May 23, 2014
Everyone seems to be talking (and writing) about "long range" hunting these days, so I guess I'll join the fray.
Most of the purpose-built rifles for hunting at extended ranges resemble military sniper rifles in size, weight and configuration: heavy-taper barrels, McMillan tactical stocks, bipods, oversized scopes with lots of magnification and target knobs — the works.
Most rifles that come in such a configuration from the factory seem to be chambered in .308 Winchester, which begs the question of whether this cartridge is up to the task of taking game at long range.
If we're going to answer this question, we must begin by clarifying our definitions. "Long range" means different things to different people, in different parts of the country. For the sake of this discussion, let's assume that long range hunting begins at 300 yards and goes out from there.
I'm not saying I agree with the ethics of taking long shots at unwounded game for the sake of it, I don't — I'm just going to tell you whether the equipment will get it done if you can. I think this is valuable information for a variety of reasons, the foremost of which is that if I wound an animal and my only opportunity for a follow-up shot is at long range, I want to be able to put the animal down for good.
There are four relevant factors in determining whether a cartridge is viable for long-range hunting: trajectory, wind drift, impact velocity, and accuracy.
Trajectory is less important than it once was thanks to the widespread availability of laser rangefinders and scopes with bullet drop reticles and external adjustment knobs, but we still want the flattest bullet flight that we can get.
Nosler's loading data for the .308 shows that a 165-grain Accubond bullet can reach a muzzle velocity of 2,820 feet per second (fps) with a max load of RL 15. At sea level, using a 200 yard zero, that projectile will drop 76 inches at 600 yards, which means 12 MOA of "come up." While dialing for 76 inches of drop is not a big chore using target knobs, it would be pretty well impossible to do with any precision using a standard reticle and no means of making field adjustments.
For comparison's sake, if we use an Accubond of similar sectional density, the 6.5-284 Norma's 130-grain Nosler drops about a foot less at the same distance. That's not a huge difference, but as the range increases, so does the disparity in bullet drop. Out at 900 yards, the .308 drops 30 inches more than the 6.5-284.
The Norma cartridge will fit on the same action length as the .308 so we are really comparing apples to apples here.
With wind speed and direction being equal, how much a bullet is affected by wind is a function of bullet construction (BC, weight, etc.) and flight time — the longer a bullet is in the air, the more time wind has a chance to have its way with it.
This time lets compare the .308 to a cartridge that uses the same parent case — the .260 Remington. With a 140-grain Accubond at 2,820 fps in a 10 mph full-value wind, the .260's shot will drift 86.5 inches at 1,000 yards.
Bullet velocity being equal, the .308 drifts only about 9 inches further in the same wind. Not bad.
When we're talking about hunting, the bullet can't just hit the animal — it must hit the animal with sufficient speed to expand the bullet and do the tissue damage necessary to put the animal down.
Nosler Partition and Accubond bullets are designed to expand at 1,900 fps or greater (most other bullet designs expand at similar velocities, but let's stick with our Accubond example for now). Our maximum effective range on game will be the distance at which the round crosses the 1,900 fps threshold.
Using Nosler data once again, we find that the 165-grain bullet falls below the velocity threshold at between 500 and 550 yards. The lighter 150-grain bullet is in the same ballpark at just over 500 yards, and the 180-grain falls below 1,900 fps at just over 400.
Here's where the capability of the cartridge runs into a wall of facts — no ballistic computer or high-dollar optic is going to make that bullet expand. Are there bullets on the market that will perform at velocities under 1,900 fps? I'm sure there are, but none that I'm aware of advertise the fact.
If we're talking about shooting game animals at long distances, we need a cartridge and rifle that are capable of consistently putting bullets into the vitals of our intended targets. Much has been written about the "inherent accuracy" of the .308 Winchester, and I actually buy into this.
That doesn't mean that every .308 will shoot MOA or better, but most rifles so-chambered have behaved well on the range for me.
Even with a gun that shoots 1.5 MOA, we're still talking 7.5 inches at the 500-yard mark where we cross below our velocity threshold — that's plenty of accuracy to get the job done on most big game animals.
The .308 Winchester is capable of the mechanical accuracy, trajectory, and wind resistance in order to make hits on big game animals at far beyond the ranges at which I intend on shooting them. Where we hit a non-negotiable barrier is the velocity threshold necessary for reliable bullet performance. In most bullet weights, that distance is around 500 yards at sea level.
From an ethical standpoint, I cannot recommend using a cartridge at distances where the bullet cannot be counted on to do its job. I'd call the .308 an adequate cartridge out to 500 yards, but beyond that you'll need to show me a bullet that will perform well at that distance.
Before you say it, yes, I am aware that the .308 has done decades of duty as the go-to sniper rifle cartridge for our military. That doesn't mean that it was the best tool for the job, and it doesn't mean that it's a great choice for shooting deer at 700 yards.