The "Modern Sporting Rifle" Fallacy

By Gary Zinn

Have you heard about the Modern Sporting Rifle? Everyone is buying them, attaching everything except cardboard pine tree air fresheners to them, and using them to shoot at everything (animate and inanimate) short of the African Big Five dangerous game animals. Did I mention they are mainly chambered for the best selling centerfire cartridge in the USA?

I am, of course, referring to the sporter versions of the AR15 rifle. The popularization of the AR15 in the civilian shooting community is clearly the most significant development in the firearms scene of the last 50 years. The rifle type, as originally developed, was designed to fire the .223 Remington commercial cartridge, which the US military and NATO call the 5.56x45mm. AR15s chambered for the cartridge are legitimately used by civilians for recreational and casual competitive shooting, serious competitive shooting, varmint hunting, home and ranch protection. Many AR15 owners, myself included, just like the rifle, because it is fun to shoot.

If one were to buy into the marketing hype, commercial gun magazines copy and Internet forum buzz, it would be easy to conclude that AR-type "modern sporting rifles" are quickly making all other types of rifles obsolete. My argument is that the implication the AR-type rifle is destined for universal dominance is a fallacy. (A polite way of saying "Bunk!").

Yes, AR-type rifles have come to dominate the autoloading centerfire rifle category, but I do not see any scenario in which they will render bolt action and lever action rifles obsolete or irrelevant, especially for big game hunting. I say this because both the AR15 and the related AR10 have physical limitations that dictate they cannot be chambered for some of the most popular and useful centerfire hunting cartridges. Further, even AR10 rifles chambered for capable and popular cartridges, such as the .308 Winchester, have disadvantages in the field that I believe will prevent them from ever becoming highly popular hunting rifles.

Limitations of the AR15 design

It should be obvious that the .223 Remington cartridge does not have the bullet diameter, weight, sectional density and downrange energy to make it a legitimate hunting cartridge for animals larger than common varmints and small predators. The solution would seem simple: use larger bore cartridges with heavier bullets of greater sectional density.

The desire for more powerful AR15 cartridges has motivated some firearms manufacturers and cartridge designers to tinker with new or modified cartridges than can be jammed into the small AR15 action. More powerful AR15 cartridges are viewed as desirable for both military/law enforcement and civilian applications.

The problem is designing larger bore cartridges that will fit and function in the confines of the AR15 receiver and magazine, while driving hunting weight bullets with enough velocity and energy to be effective for taking game animals at reasonable distances.

Here is a summary of what has been accomplished in this regard. I am not going to mention every proprietary or wildcat cartridge that has been spun off of the .223 Remington. Nor will I include cartridges that have been introduced for the AR15, but which fell flat in the market (e.g., the .30 Remington AR). No cartridge will get mentioned if its external ballistics fall far short of the .30-30 Winchester, a cartridge that I consider a benchmark for big game hunting cartridges.

There are five cartridges that have achieved some degree of success in the AR15 platform and which have reasonable potential for hunting Class 2 game. By "some degree of success," I mean these cartridges are chambered in rifles made by one or more major AR15 rifle makers and for which commercial ammunition and reloading components (cases in particular) are reasonably available. As best I can judge, these cartridges are the 6.5mm Grendel, 6.8mm SPC, .300 ACC Blackout, 7.62x39mm and .450 Bushmaster.

Data for the first three cartridges are from the on-line Nosler Load Data site, and I used Western Powders load data for the .450 Bushmaster. For each cartridge, I selected a single bullet weight that I felt represented the capabilities of the cartridge. I selected one load that gave a relatively high MV for the bullet, while fully using the powder capacity of the case (close to 100 percent load density). The one thing I could not select or standardize was the barrel length of the test rifles in which the data were developed. I note the barrel length in each case. All maximum point blank ranges (MPBR) are for a +/- 3 inch bullet trajectory and are rounded to the nearest 25 yards.

6.8mm SPC: The bullet is the 110 grain Nosler AccuBond (BC .370, SD .205). Using 27.0 grains of Accurate 2230 powder will produce MV of 2423 f.p.s. and 1434 ft. lbs. of energy from a 20 inch barrel. The MPBR is 225 yards, with retained velocity and energy of 1936 f.p.s. and 915 ft. lbs.

.300 ACC Blackout: The bullet is the 125 grain Nosler AccuBond (BC .366, SD .188). Using 18.0 grains of Lil\'92 Gun powder will produce MV of 2151 f.p.s. and 1284 ft. lbs. of energy from a 16 inch barrel. The MPBR is 200 yards, with retained velocity and energy of 1742 f.p.s. and 842 ft. lbs.

7.62x39mm: The bullet is the 123 grain Hornady SST (BC .295, SD .183). Using 25.5 grains of H4198 powder will produce MV of 2433 f.p.s. and 1617 ft. lbs. of energy from a 22 inch barrel. The MPBR is 225 yards, with retained velocity and energy of 1847 f.p.s. and 932 ft. lbs.

A note about this cartridge is in order. It is, of course, the cartridge for which the Soviet AK47 and SKS rifles were designed. While the other three cartridges were developed from scratch to fit and work in the AR15 platform, the AR15 has been adapted to accommodate the 7.62x39 cartridge. The most obvious and critical adaptation is that AR15s using the 7.62x39 have strongly curved magazines, to properly feed the highly tapered cartridges. All other viable AR15 cartridges use straight or slightly curved .223 Remington magazines, either as is or very slightly modified.

.450 Bushmaster: The bullet is the 225 grain Hornady FTX (BC .140, SD .157). Using 40.5 grains of Ramshot Enforcer or Accurate 4100 powder will produce MV of 2332 f.p.s. and 2717 ft. lbs. of energy from a 16 inch barrel. The MPBR is 200 yards, with retained velocity and energy of 1334 f.p.s. and 890 ft. lbs.

It is useful to compare the data summarized above with that for a long established cartridge that is a proven performer for hunting common Class 2 game animals, such as deer. This is the .30-30 Winchester. I include two .30-30 loads, for reasons that will become clear. The .30-30 data is from the Hornady Handbook of Cartridge Reloading (9th edition).

.30-30 Winchester (traditional): The bullet is the 150 grain Hornady Interlock RN (BC .186, SD .226). Using 35.0 grains of H335 powder will produce MV of 2300 f.p.s. and 1762 ft. lbs. of energy from a 20 inch barrel. The MPBR is 200 yards, with retained velocity and energy of 1515 f.p.s. and 764 ft. lbs.

.30-30 Winchester (LEVERevolution): The bullet is the 160 grain Hornady FTX (BC .330, SD .241). Using 37.0 grains of LEVERevolution powder will produce MV of 2300 f.p.s. and 1879 ft. lbs. of energy from a 20 inch barrel. The MPBR is 225 yards, with retained velocity and energy of 1775 f.p.s. and 1120 ft. lbs.

The first .30-30 load is essentially the one that has been used to take innumerable deer and other game for over a century. The LEVERevolution load uses a new propellant and a soft-tip spitzer bullet that together maximize the ballistic potential of the cartridge.

Overall, these powered-up AR15 cartridges fall well short of both .30-30 loads in bullet sectional density, which does not bode well for their penetration. Only the 110 grain 6.8mm SPC bullet exceeds the minimum .200 SD normally regarded as adequate for Class 2 animals. They slightly exceed the downrange energy of the traditional 150 grain .30-30 load and fall short of the LEVERevolution .30-30 load.

These four AR15-compatible cartridges promise similar, but not more spectacular, results in the field when compared with the traditional .30-30. In summary, I would judge these cartridges to be generally as capable as the traditional .30-30 on Class 2 game out to about 200 yards, but I would not recommend them for hunting larger or tougher game animals for which the LEVERevolution and traditional 170 grain .30-30 loads are suitable.

The 6.5mm Grendel is currently the only AR15 platform cartridge that is more than marginally impressive from a big game hunting perspective. The 6.5mm Grendel, developed and promoted by Alexander Arms, is based on the 6mm PCC case.

I compared a 6.5mm Grendel factory load with a .260 Remington factory load to put its performance in perspective. Both factory loads had MVs quoted for 24 inch barrels, which I adjusted to 20 inch barrels. The MPBR values, rounded to the nearest 25 yards, are for a +/- 3 inch bullet trajectory.

6.5 Grendel: Hornady Custom load with 123 grain Hornady SST bullet (BC .510, SD .252), MV 2500 f.p.s. The MPBR is 250 yards with a retained velocity of 2095 f.p.s. and energy of 1199 ft. lbs.

.260 Remington: Federal Premium load with 120 grain Nosler Ballistic Tip bullet (BC .458, SD .246), MV 2870 f.p.s. The MPBR is 275 yards with a retained velocity of 2338 f.p.s. and energy of 1457 ft. lbs.

Although clearly inferior to the .260 Remington, the 6.5 Grendel is superior to the AR15 cartridges previously discussed. The Grendel has a better resume as a hunting cartridge than the 6.8mm SPC and 7.62x39mm, while the .300 ACC Blackout and .450 Bushmaster are not even in the same league. If I were going to buy an AR15 rifle for deer hunting, it would be a 6.5 Grendel.

The AR10 -- good news / bad news

The AR10 platform is spacious enough to handle modern short action cartridges that the AR15 cannot. Since the AR10 was purpose-designed to fire the military version of the .308 Winchester cartridge, it can be readily adapted to handle any of the commercial derivatives of the .308. I did not have to look very hard to find AR10 models offered by one or more commercial manufacturers in .243 Winchester, .260 Remington, .308 Winchester and .338 Federal. Not presently on the market, but feasible, would be AR10s chambered in 7mm-08 Remington and 6.5 Creedmoor (which is virtually identical to the .260 Remington).

The four cartridges currently chambered in AR10s certainly expand the hunting potential of the rifle. I can say this without even quoting the ballistics data. With loads suitable for deer and other Class 2 game, MPBR distances, terminal velocity and energy are significantly increased over the best AR15 cartridges.

Moving up to the smaller Class 3 game animals, the .243 Winchester goes out of play, but I would not question the range and terminal performance of appropriate loads in the other three cartridges. For large Class 3 game, the .308 Winchester and .338 Federal, throwing heavier and sturdier bullets, are still legitimate.

Incidentally, the .338 Federal may be the best cartridge you never heard of. Consider a cartridge firing a 210 grain Swift Scirocco bullet (BC 0.507, SD 0.263) at 2550 f.p.s. MV and 3032 ft. lbs. ME from a 24 inch barrel. This round has a +/- 3 inch MPBR of 250 yards, with 2138 f.p.s. and 2132 ft. lbs. of retained velocity and energy. Think about it.

That was the good news regarding the AR10 as a hunting rifle, but there are three items of bad news. First, the AR10 cannot accommodate long action cartridges, so the .30-06 and its derivatives are out of play, as are popular magnums, such as the 7mm Rem. Mag., .300 Win. Mag. and .338 Win. Mag.

(As an aside, if one wants an autoloading hunting rifle with more caliber choices, consider the Browning BAR. BAR variants are available in .243 Winchester, .25-06, .270 Winchester, .270 WSM, 7mm-08, 7mm Remington Magnum, .308 Winchester, .30-06, .300 WSM, .300 Winchester Magnum and .338 Winchester Magnum. This is an impressive selection of very capable cartridges.)

Next, AR10 rifles are on the heavy side. The AR10s for which I found specifications were generally listed as weighing eight pounds or more (empty, without scope and mounts or sling). The lightest one I noticed was the Remington R-25 GII, listed at 7-5/8 pounds in .308 Winchester with a 20 inch barrel.

The weight of a field ready rifle will typically be 1.5 pounds or a bit more than the bare rifle weight. Starting with an eight pound AR10, a 3-9x40mm scope mounted in high rings, a sling and ammo will likely bring the field carry weight up to 9.5 to 9.75 pounds. If one carries that rifle over hill and dale all day, by evening it will feel twice as heavy as a rifle that actually weighs one or two pounds less. By comparison, there are several major brand, bolt action hunting rifles with 20 inch barrels that weigh 6.5 pounds or less (bare). (See Compact Bolt Action Deer Rifles.)

My final point about using AR rifles in the field is qualitative. ARs carry, handle and balance differently than conventional rifles. Whether carried slung over the shoulder or in the hands, the pistol grip and magazine sticking out of the underside of the rifle and Picatinny rails often slathered all over the rifle may get in the way. Regarding handling, the pistol grip gives a very different feel from conventional rifle grips and slows mounting.

As for balance, every AR I have used with a 20 inch or longer barrel had a noticeably forward balance and felt muzzle heavy. These handling and balance deficiencies are things with which a shooter needs to become comfortable.

As a compromise between handling and ballistic performance, I believe that an AR rifle used for hunting should have a 20 inch barrel. A 24 inch barrel is just too weight forward to handle well, while a 16 inch barrel unacceptably degrades the ballistic performance of whatever cartridge is being used.

I have one piece of "do-not" advice regarding slings. There are some AR slings that use a length of elastic as a component. Do not go there! Many years ago, I bought a rifle sling that had built-in elastic. It was touted as being shock absorbing, but I found out in one day afield that it actually was a bungee cord for my rifle. The rifle bounced every time I moved and I wore myself out keeping it under control. I never used that sling again.

The observations made about carry weight, handling and balance of AR10s also apply to AR15 rifles. The only difference is that bare AR15s will generally weigh less than AR10s. For instance, Alexander Arms makes a rifle chambered in 6.5 Grendel that weighs 7.5 pounds with a 20 inch barrel. A lightweight model with an 18 inch barrel is listed as weighing 6.5 pounds. I dislike the weight of the first rifle and the too-short barrel on the second one. The tradeoff is problematical either way.

Here is an illustration of how ridiculous the AR modern sporting rifle theme has gotten. A major AR builder has put a lightweight 16 inch barrel and lightened hand guard and gas block on their AR15 platform. They call it a "Lightweight Mountain Rifle" at 6.2 pounds, bare. It is chambered in .223 Remington; I guess it is a marmot mountain rifle.

A modern sporting rifle, not THE modern sporting rifle

The thing that disturbs me about AR-type rifle promoters touting them as "modern sporting rifles" is the implication that the term is exclusive to those rifles. I acknowledge that AR rifles are modern, in the sense that they feature a relatively modern (half century old) operating system with aluminum receivers and plastic stocks. However, does that make them more modern than a stainless steel bolt action rifle with a composite stock? I think not.

Moreover, it would be silly to think of the AR-type rifle as THE modern sporting rifle when it cannot be chambered for a significant number of the more capable commercial cartridges. Add to this the fact that AR rifles are relatively heavy and many shooters may find them poorly balanced and awkward to maneuver and the case for exclusivity becomes very weak, indeed.

An AR-type rifle may be referred to as a modern sporting rifle, but so are bolt, lever and more conventional autoloading rifles that are made using modern materials and production techniques. In my opinion, no action type has an exclusive claim to the label "modern sporting rifle."

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Copyright 2016 by Gary Zinn and/or All rights reserved.