Building the Impossible – The Elusive One Gun for Everything

For many years it’s been a focal point for minimalists to have a single gun that can be counted on for all the major tasks. It’s an exercise in futility in some respects of course because when you start buying guns, it gets very hard to stop adding to the collection whether it is a rifle, shotgun, or handgun. But with the AR it’s different.

You can easily accessorize to create a firearm that uses a core set of components paired with say, an upper receiver kit to help you accomplish a lot more, with what is essentially an add-on component. 

Two Paths You Can Go By

This article was always going to be controversial to the hardcore builders. Opinions aren’t generally formed without reasoning behind them. Many people are going to disagree with the premise of the article, if not the choices, but it should be seen as a thought exercise that helps you to get thinking about how you can accomplish similar goals for yourself. 

And there are two schools of thought when you bring up the “one gun” concept. The first is a single gun, a single cartridge, with multiple potential use cases. Generally, this methodology is seen as the most bang for your buck if you had to run an AR but had to squeeze as much potential as possible out of it and that you didn’t have time in between uses to think about doing any changes – you just open the gun safe, and the gun is ready to do what you need it to do. 

That’s a big ask of a firearm, considering how many guns the average AR owner now seems to keep in their collection. Many gun owners get the itch, and they don’t stay single gun owners for very long. 

So, how would you approach something like this? Here’s a solid option.

The setup:

One Gun; one cartridge; multiple loads, multiple use cases

.300BLK with a suppressor and a 16” barrel (requires a tax stamp and an extensive background check)

The use cases where it can shine:

Home defense; hunting of larger game; hunting of smaller game; depredation; target shooting, plinking, suppressed use; CQB and duty needs

Why it makes sense:

The intermediate game capabilities and the duty/CQB benefits of mitigating a lot of friendly fire and second target hit probability are incredible. The ability to suppress the sound is a huge quality of life benefit and the ballistics, while not best in class, are more than adequate for all the situations listed above. It is a workhorse option considering the ballistic capabilities of the subsonic and the supersonic rounds combined. 

The small overall size of the package needed to deliver terminality for game or defensive targets lends well to the idea of being more mobile and capable as a shooter. 

The cost of the cartridge is not too radical, and the reloading components are readily available. With the right handloads, you can achieve very competitive options to push the limits even further. 

Why not something else?

No other cartridge has the same broad spread of use cases and has been proven to be so good on the fine points. Some other cartridges could potentially do just as well, but they lack some of the polish that the .300BLK can bring to the table in this instance. 

Namely, the 6.5 Grendel or the 6.8SPC, or the .300 HAM’r, could all do a lot of what the .300BLK in subsonic and supersonic can achieve, but you wouldn’t have nearly the stealth that the suppressed .300BLK offers.

Additionally, you wouldn’t get nearly the safety benefits when used indoors, which is a very important benefit of the .300BLK in CQB (close quarters battle).

The .223/5.56 could be used well in a home defense scenario if the right load was selected and it would probably match the .300BLK in mitigating second target hits after a first target hit during a defense situation, but it wouldn’t be able to be suppressed as well as the .300BLK. 

The ballistics of the .223/5.56 isn’t going to be on par with the others on the list either, so you wouldn’t be able to move up a step-in game species. Additionally, the long-distance benefits of the other cartridges are superior, including the accuracy, though the .223 is a bit more accurate than the .300BLK.

Some CONS:

The trajectory isn’t spectacular on either type of load, whether subsonic or supersonic in relative comparisons, and it is a bit of a Jack of all trades, and not a specialty use round, outside of the sound suppression task and the CQB benefits. Additionally, the accuracy of the round is not spectacular when pitted against any of the alternative rounds mentioned above. 

If a suppressor was out of the equation, it may not have scored so highly, relative to peers. This build almost necessitates a suppressor to extend the use cases. 

The Second School of Thought

The second school of thought on the “one gun” concept is the idea that the AR was meant to be deployed quickly, but that all the versatility shouldn’t be locked up by some esoteric idea that you can’t change an upper receiver. After all, it takes a few seconds to pull some pins and push another upper receiver onto the lower.

With the right optics setups, you can work wonders with a setup like this, but make no mistake – it’s going to start adding up quickly and your wallet may not like it.

Additionally, it’s an exercise in analysis and parts-picking that will take you down the rabbit hole of the vast AR ecosystem and that means you are going to spend a lot of time engaged in the concept of it all. 

Here’s a baseline concept that may help give some direction and save a bit of time.

The setup:

• One gun; multiple upper receivers to complete the package and multiple loads to ensure proper execution on your gameplan; multiple use cases
• 5.56/.223 base rifle with a 16” barrel 
• Upper conversion for a 6.5 Grendel with a 20” barrel
• Upper conversion for a .458 SOCOM with a 16” barrel

You could swap the 6.5 Grendel upper with a .300 HAM’r or a .350 Legend Upper if you prioritize hunting and don’t need to shoot past 400 yards and need a larger diameter bullet to bridge the gap.

It should be noted that with the right loads, a .458 SOCOM could be dialed up or down to achieve similar results, albeit with nowhere near the accuracy of the .300 HAM’r.

The use cases where it can shine:

Each of these platforms when assembled onto the lower receiver has its niche placements. The 5.56/.223 is great for home defense and can mitigate friendly fire concerns with the right planning and load selection. 

The .458 SOCOM gives big-bore stopping power in the field, especially in a heavy brush landscape, and can be used to hunt game to 1000+ lbs. The size and engineering of this cartridge can also put it into a duty level of performance for unique situations where shooting through a barrier will be important. 

The 6.5 Grendel puts you out past 750 yards and probably into 850 accurately and gives you enough power for an elk-sized game pretty easily in good conditions. Its accuracy is exceptional. It, too, can be used for defensive purposes. 

Why it makes sense:

Choice trumps everything if you have the time to make the choice. In this case, this gun will do 95%+ of the things you would want to with an AR, or any handful of firearms. The only thing this setup doesn’t do well is concealment. 

When you think about adding a 4th option to further expand the middle segment of options on this system, it becomes even more powerful – again the only drawback is that it’s going to cost you a lot. 

Why not something else?

Why would you need anything else?

Some CONS:

Expensive. Takes time to swap out uppers and accessories to optimize the experience. Because of varied use cases, optics may be so different as to push costs up further and make it hard to dial in between changes.

Wait a minute. Why are we only talking about the standard AR-15? Wouldn’t it make a lot of sense to include a build for the AR308 pattern? After all, that’s one way to push the AR into an intermediate class weapon system by default before you even must worry about accessorizing, picking top ends, or optimizing for multi-use crossover situations. 

That’s not incorrect, and the .308 pattern for the AR is a compelling build option, especially when you consider the ability to use much larger cartridges. 

Here’s a buildout for consideration.

What About A .308 AR-15?

The setup:

• One gun (based on the larger AR308/AR-10); multiple upper receivers to complete the package and multiple loads to ensure proper execution on your gameplan; multiple use cases
• .308 Winchester base rifle with an 18” or 20” barrel 
• Upper conversion for a 6.5 Creedmoor with a 22” barrel (or longer)
• Upper conversion for a 5.56/.223 with a 16” barrel (requires a magwell conversion because the larger AR has a much larger magwell)

The use cases where it can shine:

This system can do anything. It’s a very robust and wide-ranging setup that can go from tiny animals and basic defensive use to 1000+ lbs. game targets out to about 1k yards. You will need some serious glass to get there though, so plan accordingly.

This is the best hunting setup in this article, if you need premium long-distance potential, though it may not be able to handle 100% of the game in North America. The .308 is going to hit a bit of a wall of limitations when you get to the biggest game, though some shots will be possible.

The 6.5 Creedmoor has the power and the velocity too, under certain conditions, but the wound channel is smaller, and the heft of the projectile may not offer enough for bear or large moose, etc. 

In home defense, you could opt for .308 if you have no friendly fire concerns; or 5.56, which can make it a bit safer for second target hits, while still providing adequate ballistics for a defensive target. 

Duty potential is there from sharpshooting long-range precision with either of the bigger calibers to CQB with either the .308 or the 5.56.

The .223 makes it reasonable to shoot at targets and on small game up to deer-sized game. 

Why it makes sense:

Because it’s got all bases covered. 

Why not something else?

This is the most comprehensive setup on this list, it’s hard to knock it from a capability perspective. Possibly you may not want this setup because it could be overpowered for your needs. 

Some CONS:

It’s expensive to build this platform setup. Expensive to shoot this group of cartridges if you aren’t leaning heavily towards the .223/5.56. Heavier, bulkier, and the magwell conversion that is needed may introduce more components that could be broken or may need to be serviced. 

Wait, What’s this Going to Cost Me?

Well, that’s up to you, but you can roughly equate it to buying a standard baseline firearm when you add an upper receiver conversion. What does that mean? You are basically paying within 15% of the same price as what it would cost to replicate the purpose of the gun on a standalone platform, and that could mean 15% more, or 15% less, and within that range generally. The component mix and specialized options steer that price. 

Let’s get some clarity here. If you were to buy a 308 Pattern AR, in .308, and then you wanted to add a 6.5 Creedmoor upper, that upper would range about $550 – $750 for a basic option (and more depending on brand name and component mix).

Similarly, you could buy a Savage 110 in 6.5 for about $750; and a Ruger Precision in 6.5 Creedmoor for about $1500. These two rifles represent different ends of the spectrum. So comparatively, you can see that the upper conversion for your AR in 6.5 Creedmoor is within that 15% difference range of that baseline rifle by Savage.

Of course, you can spend more or less depending on components and brand. There are plenty of configurations that could push an upper receiver in 6.5 Creedmoor to that $1500 price point as well. Spending money on gear is never as important as training.

This should serve as a pretty good rule of thumb. 

Why the AR is the only option that can even come close to a one-gun concept

The upper receiver add-on capability is a huge part of the “one gun” concept because it’s fast, accurate, and easy to implement. It’s approachable, built to standardized specifications and drop-in. This plug-and-play mentality means that once you have properly headspaced your components in the bolt/breech, or if you buy a fully factory-built upper, you have a new application immediately. 

The proliferation of tools, components, parts, accessories, and replacement parts and upgrades makes the AR the perfect palette for this firearm concept. 

The broadness of the spectrum of what can be accomplished with the AR is an important factor. A bolt action in .30-06 Springfield, you have a small spectrum of use cases – generally target shooting and hunting large game.

With a .22LR Lever action, generally plinking or small game hunting and some generic uses. With a 1911 in .45ACP, self-defense, slim carry, and maybe some home defense stuff, or some light competition use.

The AR can be outfitted to handle LE/Duty use, military needs, home or personal defense, target shooting or competition, and hunting, from small game and varmint to very large game depending on conditions and cartridge selection. 

Value for money spent is big with the AR if you aren’t going crazy on every single component. If you are building a mainstream AR, you can expect to get a lot of value because parts are not expensive unless you opt for ultra-premium or branded specialty components.

Part of this is because they are mil-spec, contract-produced items for a lot of the pieces and that they are widely available, and mass produced for years.

Size, weight, and mobility are crucial variables, and the AR offers a potential for a lower weight, highly efficient, and highly capable system in a carbine-sized gun, or a gun that can be as big and heavy as you want it to be.

Having the option for high power and low footprint with moderate to low weight makes it versatile. You can make ultra-lightweight versions easily too. 

Caliber and cartridge options and market attention to development over the long-term is probably one of the most important aspects of this argument. The idea that an AR isn’t just a .223/5.56 but could go much higher and even a bit lower in the range of cartridges and calibers is special.

The unimpacted, basically inert state of the lower receiver group means that recoil and other gun variables don’t factor into the parts comprising about half of the gun, generally. Sure, there can be some issues with the buffer system depending on the build, but generally, the ability to slap a very powerful option on top of a lower that isn’t involved with the operation of the gun in all ways makes it versatile. 

What do I really need it to do? What are the realistic synergies that I can find?

• If it can kill big game, it can kill a dangerous man-sized threat
• You’re at 2 MOA you can hunt with it easily and you’re at better than mil-spec generally and most AR builds are 2.5MOA or better out of the box
• With a monolithic optics mount, or choose to use properly indexed quick-release optics mounts, you can return to zero on guns pretty easily, even when swapping out uppers
• Controls are the same, so you can outfit them for the most intense scenario you envision (probably personal defense) and learn them easily for all other scenarios, like target shooting or hunting
• Barrel length can be a huge equalizer if you want to be in the hunting game because you can optimize projectile stabilization and velocity deviation – you can also forgive a few more inches of barrel length by using the right buttstock to adjust the length of pull, or provide a balancing weight, etc. 

Will I only need one load? 

 Not only will it be impossible to fuel a “one gun” with a single load, but you’re also going to be lucky to get away with 2-3 extra top-ends on an AR. Although, if you take the appropriate measures, a properly outfitted .300BLK or .308 Winchester rifle could genuinely function as a “one gun” it would require multiple loads.

Loads will vary based on strategic use cases, and while you can find some carryover, you really need to be flexible with the minimalistic concepts when you are trying to build the one gun. It seems counterintuitive to have one gun that can do it all, that still needs multiple setups to accomplish the one-gun title.

What is realistic, possibly, is to find a single load per upper/cartridge you decide on. If you’ve chosen to go down that path, a single load for hunting big game, say on the 6.5 Creedmoor, and a different load for the .308 for home defense, and a third load for .223 which could be achieved by adding the magwell block and a suitable upper conversion to allow for small game hunting and cheaper overall target work thanks to the .223’s favorable cost basis

There’s more to the story, still

If you’re striving to have a single gun that can get you out of anything or provide exceptional coverage for all your normal shooting and sporting needs, you are going to want to consider it’s about a mindset, a strategy, and a well-executed plan more than it is about a single gun.

What about wear and tear, frequently replaced parts, matching loads to barrel twists, or optics to different targets? Think monolithically, but also think about how modularity will play a role. 

Half of the battle when finding the holy grail of the “one gun” is to keep the components running and keeping the maintenance and accessorizing to a balanced level to ensure you can accomplish what you set out to do in the first place. Happy building!