What Is the Best All-Around Big Game Bullet Diameter?

If you’re primarily a varmint hunter, deer hunter or target shooter, then versatility doesn’t mean much to you. I’m all of the above, but none exclusively. When I say I want a versatile, “all-around” caliber and cartridge, I’m not thinking about prairie dogs or about competitive disciplines. I’m not always hunting, but I’m always a hunter, so I’m thinking beyond paper and steel targets. Deer-size game comes first, which includes pronghorns and gazelles in open plains, and sheep and goats up in the rocks. Big bears and thick-skinned game are excluded as specialized pursuits, but I include elk, caribou, red deer, even moose—plus larger African plains game.

In that context, we can cut the field down to just five bullet diameters or calibers. They are: .257, .264/6.5mm; .277/6.8mm, .284/7mm and .308. Arbitrarily, I am ignoring all bullet diameters above .308. They have their uses, but with today’s great bullets they aren’t essential until you get to game larger than black bear, elk and moose.

I have used all five diameters in various case dimensions, thus at various velocities and with multiple bullet weights. Some of you may have greater experience, and maybe you like all these calibers equally, but I doubt it. Most of us have our favorites. There are quarter-bore fans, like my old friend Bob Milek and editor Scott Rupp. Today, thanks to the 6.5 Creedmoor’s popularity, there are now legions of 6.5mm fans.

Jack O’Connor’s writing lured generations to the .270. In turn, Les Bowman and Warren Page led us to the fast 7mm. In America, the .30 caliber needs no high priest. It started with the .30-40 Krag and .30-30, continued with the .30-06 and went on to the magnum .30s. I have my favorites, and it’s okay for you to have yours. My purpose here is to try to examine the differences.

How we settled on these specific diameters isn’t clear. In cartridge nomenclature, we tend to round bullet diameters. British and sometimes American manufacturers confuse the issue further by using the smaller land-to-land bore diameter, rather than groove-to-groove or bullet diameter. So the .256 Newton used a .264 bullet; the .275 Rigby and .275 H&H used .284 bullets.

The .25 caliber is the least confusing. It started in 1895 with Winchester’s .25-35 using a .257-inch bullet. Metrically speaking, it’s 6.53mm, but all “.25 caliber” cartridges have used .257 bullets.

I wish the rest were so simple. Several early 6.5mm military cartridges specified a .263-inch bullet. The first .264-inch cartridge was Italy’s 1891 6.5x52 Carcano. Since then, 6.5mm has meant .264-inch bullets. However, the actual conversion is that .264 inch equals 6.71mm, not 6.5.

No one knows exactly where Winchester came up with a .277-inch bullet in 1925. It doesn’t matter; the .270 Win. was a stunning success. The .270 Wby. Mag. and .270 WSM also use .277 bullets. In 2002, Remington used “6.8mm” to name its 6.8mm SPC, and Winchester kept the same designation for its 6.8 Western. The real origin may be an experimental 6.8x57 Mauser cartridge, but “6.8mm” was never literal: .277 inch equals 7.04mm.

The ”7mm” with a .284-inch bullet goes back to the 7x57 in 1892. Over time, its success solidified .284 inch as the standard diameter for a 7mm. Except, again, the conversion doesn’t add up: .284 inch does not equal 7mm. Actually, it’s 7.21mm.

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Early “.30 caliber” cartridges varied in diameter. Russia’s 7.62x54 called for a .310-inch bullet, and the .303 British and 7.7mm Arisaka used .311-inch bullets. It was American .30 calibers that made .308-inch bullets almost universal. However, .308 inch is not actually 7.62mm. The correct conversion is 7.82mm. John Lazzeroni catches guff for his offbeat cartridge names like 7.82 Warbird, but they are literal and precise. Let’s take a look at each of the five “all-around” bullet diameters, trying to be objective.

.257

Although it’s almost impossible to quantify, I believe in frontal area for energy transfer. Paper and steel targets don’t care, but impact matters greatly on game animals. Bullet design and performance are critical, but raw bullet weight or, better, weight to caliber, matters. Just .007 inch separates the .257 from the 6.5mm (.264). In frontal area, this is too close to call.

The quarter-bore offers our first example of the essential synergy among calibers, case dimensions, velocity, bullet weights, rifling twists, action lengths and downrange performance. Aerodynamically challenged by blunt bullets in tubular magazines, the .25-35 was a great success.

In 1915, Arthur Savage engaged Charles Newton to build a new, fast cartridge. Using the .25-35’s .257 bullet, the result was the .250-300 (.250 Savage), the first commercial cartridge to broach 3,000 fps. It could do this only with light 87-grain bullets, and 1915 bullets weren’t up to that velocity. When they worked, they dropped game like lightning, but sometimes they came unglued.

Hunters quickly learned heavier bullets delivered more consistent performance, albeit at lower velocity. There is another legacy to the .250 Savage. Initially, barrels were a slow 1:14 twist, unable to stabilize bullets over 100 grains. In 1920, Savage changed the twist to 1:10, the common twist for .25s ever since.

The .25s have long been considered the largest “crossover” varmint/deer cartridges. The 1:10 twist will stabilize bullets from 60 to 122 grains. Heavy .257 bullets are awesome for deer-size game but light for elk. Bullets in .257 weighing above 122 grains almost don’t exist because rifling twists don’t support them.

The fastest .25s (.25-06 Rem. and .257 Wby. Mag.) shoot wonderfully flat, but they are not exceptional at long range. Years ago, I was hunting pronghorns with Winchester’s Mike Jordan. We had a wounded buck shot with a .25-06, gaining ground, wind all over the place. Mike couldn’t get him down, so he asked me to step in with my .270. Later, Mike commented, “.25s just don’t hold up in the wind.”

There’s a reason. Most .25 caliber spitzers in the 115- to 120-grain range have G1 ballistic coefficients up to about .390. On that day, I was shooting a 140-grain AccuBond in my .270, which has a G1 BC of .460. That’s not super-high by today’s standards, but it’s high enough to make a difference on a windy day.

.264/6.5mm

Thanks to the Creedmoor’s popularity, the 6.5mm is the new wunderkind. Bullets in this diameter have always been relatively long and heavy for caliber, and early 6.5mm rifles used fast twists like 1:8, stabilizing bullets from 95 to 160 grains. Early 6.5mm cartridges made their bones with 156- and 160-grain bullets. With solids delivering unprecedented penetration, they were used for game up to elephant, and I saw a Cape buffalo taken cleanly with a single 160-grain softpoint.

Mild 6.5mms like the .260 Rem and 6.5 Creedmoor are marvelous deer cartridges and wonderful for long-range target work. Faster cartridges like the 6.5-.284 Norma and 6.5 PRC deliver more energy and are more versatile. Their collective problem: For larger game, we have forgotten about bullet weight as part of the equation.

Oddly, the .264 Win. Mag. had a 1:9 twist, questionable for 160-grain bullets. Newer 6.5mms have faster twists and will accommodate longer, heavier bullets, but almost nobody shoots them.

 The Creedmoor sparked 6.5mm bullet development, and we now have great, low-drag 6.5mm bullets with off-the-charts G1 BCs up into the .600s, but weights pretty much stop in the mid-140s. The reason is simple: action length. There’s no point in developing a bullet that existing rifles won’t support due to rifling twist or action length. The .260 Rem, 6.5 Creedmoor, 6.5-.284 Norma and 6.5 PRC are short-action cartridges and are limited in terms of cartridge overall length.

Many 6.5 PRC shooters go to standard-length actions in order to use longer or heavier bullets, but aerodynamic choices are few.

The .26 Nosler is a standard-action cartridge. Nosler makes a 150-grain AccuBond Long Range 6.5mm with awesome G1 BC of .634. The company’s most recent Nosler Reloading Guide No. 9 doesn’t list data for this bullet with any other 6.5mm cartridges. There’s no point, because they will exceed max overall length in most rifles.

So, most of us (me included) shoot 140-something bullets in our 6.5s. Depending on range, these bullets are elk-capable, but short of generous. Not everyone agrees, but a 140-grain bullet is on the light side for elk, and I’ve seen issues with larger African plains game. For genuine versatility, I want more bullet weight.

.277/6.8mm

Since 1925, the .270s have been trapped by their 1:10 twist. References suggest a 1:10 twist in a .277 barrel will stabilize bullets from 100 to 160 grains. Maybe, but bullet length matters more than weight. In .277 with 1:10 twist, stabilization is about done at 150 grains. Nosler makes a 160-grain Partition, but it’s a semi-spitzer, kept short enough to stabilize in the 1:10 twist. Federal’s .277 Terminal Ascent is 136 grains, and Hornady’s .277 ELD-X is 145 grains. In both, bullet length approaches the limit of stabilization for a 1:10 twist.

So traditional .270s max out at about 150 grains. Whether with 130-, 140- or 150-grain bullets, the .270s are wonderful cartridges for deer, sheep and goat. All three of these weights are adequate for elk, but not generous.

When I was young, I had grave reservations about the .270’s adequacy for elk. I was mostly wrong, but not completely. Even 150 grains isn’t much for game four times the size of an average deer. Frontal area is another subject. No one can say how much diameter increase is needed to make a noticeable difference. Just .013 inch separates the 6.5mm from the .270. Enough to notice? I can’t prove it, but I have long believed the .270s hit harder than the 6.5s—with similar bullet weight and velocity.

The .270s have always been hampered by rifling twist, limiting bullet weight. The .27 Nosler solved that, calling for a faster twist and heavier bullets. Winchester’s 6.8 Western was a parallel development, with faster twist, together creating heavier bullets never before possible in .277.

.284/7mm

Only .007 inch separates .277 from .284 in frontal area, which is unlikely to make a visible difference in impact on game. So if bullet weights and velocities are similar, performance on game should also be similar. While it’s hardly definitive, I took 10 plains game species with a 6.8 Western, and my impression was it performed exactly like the 7mm Rem. Mag., with heavier bullets.

Remington was long the 7mm’s champion. The company settled on 1:9.25 twist for the .280 in 1955 and kept it for the 7mm Rem. Mag. in 1962. It maintained that twist for Remington’s 7mm rifles that followed—until recently. This twist is okay for 175-grain bullets, but just barely. (Incidentally, the 7x57, introduced in 1892 with 173-grain bullet, started with a 1:9 twist.)

As with 6.5mm rifles and 160-grain slugs, who actually shoots 175-grain bullets in 7mm today? We usually go with lighter bullets because they’re faster, more impressive on paper and kick less. Sixty years ago, Jack O’Connor wrote that the new 7mm Rem. Mag. wouldn’t do anything his .270 couldn’t do. Considering the minuscule difference in frontal area and with 140- or 150-grain bullets, he was absolutely right. But if you add 20 percent bullet weight, there’s a difference.

The .28 Nosler changed the game, and the brand-new 7mm PRC changes it more, both specified for faster twists. The PRC calls for a 1:8 twist, and its cartridge overall length requires at least a standard-length action. The 175-grain bullets are no issue, but both cartridges are focused on the newer, low-drag, extra-heavy .284 bullets of 180 grains and more. These are weights that had not existed in 7mm, and with BCs no one never imagined. Hornady’s 180-grain ELD has a G1 BC of .796. Good Lord!

The effect of a 180-grain, 7mm bullet on larger game is impressive. In one African camp, several camp-mates used Gunwerks rifles in the proprietary 7mm LRM, which is similar to the new 7 PRC. They were all shooting 180-grain bullets, and the results were amazing.

.308

The all-American .30 is not the king, but it is a versatile and effective bullet diameter. I admit I’m a .30 caliber guy, but .30s aren’t essential for deer-size game. Oh, they work, and bullets from 180 grains up are better for larger game than smaller calibers. Back to my frontal area theory, .024 inch separates the .284 and .308, and this difference matters. No one can say a 7mm hits as hard as a .30.

However, as 7mm fans have long told us, heavy 7mm bullets with greater sectional density penetrate better than .30s of similar weight. Take the 175-grain 7mm versus 180-grain .308. The 175-grain 7mm has an SD of .310. To equal this in .30, you have to go up to 208 grains (SD .313). The 1:10 twist has long been the standard for .30 caliber cartridges. In this diameter, twist is not a problem. A 1:10 twist will stabilize .308 bullets from 100 to 220 grains.

A century ago, 220-grain roundnoses were common .30-06 hunting bullets. As with the heaviest 6.5 and 7mm bullets, few of us have used them for many years, but their effect on larger game was legendary.

Today, thanks to low-drag bullets and the thirst for higher BCs, heavier .30 caliber bullets are again in vogue, with target bullets up to 250 grains. A 1:10 twist cannot stabilize such bullets. In order to use them, some people rebarrel, others build guns. The .30 Nosler and .300 PRC call for a faster twist—1:8 or 1:8.5. Since I believe in bullet weight, I’ve switched to aerodynamic 200-grainers in my older .30s, and I’ve been shooting bullets up to 225 grains in the .300 PRC.

The problem is heavier bullets produce more recoil, and not everyone is comfortable with .30 caliber kick anyway. For versatility that includes game larger than deer, it appears that the new .27s and 7mms, with faster twists and ability to use heavier bullets, are the way to go.

However, if recoil is an issue, keep in mind the physics of equal and opposite reactions. If gun weight and velocity are similar, then bullets of like weight produce similar recoil. A .27 Nosler or 6.8 Western with 162- or 175-grain bullet kicks the same as a 7mm Rem. Mag. with those bullet weights. A .28 Nosler or 7mm PRC with 180-grain bullets kicks like a .300 Win. Mag. with 180-grainers. Performance is great, but you can’t have it without pain.

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The Smaller Diameters

All-around suitability depends on what you want to do. The .204 Ruger is my favorite varmint cartridge. A tack-driver on paper and devastating up to coyotes, its bullets are too light for deer-size game.

Similarly, with bullets up to 90 grains in faster-twist barrels, the .22 centerfires are generally legal and often used for deer today, offering more range and deeper penetration than ever before. But the wisdom of using .22 centerfires for deer will always be debated. I will use them on medium-size deer with caution, but I won’t use them for body shots on big hogs.

The .243 Win. remains the most popular 6mm. It’s accurate, easy to shoot and a fine deer cartridge. The 6mm Creedmoor adds a new dimension to this diameter. Its shorter case allows longer bullets in a short action, plus specifications call for a faster twist to stabilize these bullets. Hornady’s 6mm 108-grain ELD-Match has an amazing G1 ballistic coefficient of .536, previously unthinkable in a 6mm bullet.

Elk and black bears are taken cleanly every year with various 6mms, but just because some folks get away with it doesn’t mean it’s sensible. The 6mms aren’t enough gun for game larger and tougher than deer.