.458 SOCOM Ammo

Best .458 SOCOM Uppers

Are you looking to build your first AR chambered in .458 SOCOM?

If so, you’ve got quite the project ahead of you. There are an abundance of parts available for the AR in popular calibers such as 5.56x45mm NATO, .308 Winchester, or 6.5 Creedmoor. But finding the parts you need to build an AR in .458 SOCOM is going to be a bit more challenging just because it’s a rarer round with fewer available parts and accessories.

Nonetheless, the .458 is an impressive round in its own right and you shouldn’t give up on building one just because there are less parts available. The .458 has stopping power very similar to that of the powerful and venerable .45-70 Government round… which means that when used within moderate distances, it can bring down any kind of big game in North America.

The first component you will need to build your .458 SOCOM AR is an upper receiver, and that’s what we’re going to talk about today. After looking through all of the options, we have narrowed down our list to the top three .458 SOCOM upper receivers on the retail market today.

We’ve also included more information on the benefits of the .458 SOCOM round, and a buyer’s guide outlining and discussing what you will need to look for in an upper receiver as well. Remember that the .458 SOCOM is a powerful round, and it requires a quality and durable upper receiver to handle it.

Our Picks For The Best .458 SOCOM Upper Receivers

Best Overall Pick

Cross Machine Tool Co., Inc. AR-15 CMT Billet Upper Receiver .458 SOCOM

Cross Machine Tool Co., Inc. AR-15 CMT Billet Upper Receiver .458 SOCOM
The CMT Billet Upper Receiver from Cross Machine Tool Co. strikes the right balance between being a fully stripped and complete upper, meaning it comes with an array of features but still leaves you room to customize. It’s also incredibly durable and designed to offer your .458 AR the very best possible performance.
See at Brownells

Best Value Pick

Cross Machine Tool Co., Inc. AR-15/M16 .458 SOCOM Billet Upper Receiver

Cross Machine Tool Co., Inc. AR-15 CMT Billet Upper Receiver .458 SOCOM
The Cross Machine Tool Co., Inc. is a solid basic upper receiver that can handle other big bore AR-calibers and not just the .458 SOCOM. It’s durable, simple, and gets the job done.
See at Brownells

Best Budget Pick

Anderson Manufacturing .458 SOCOM Stripped Upper Receiver

Anderson Manufacturing .458 SOCOM Stripped Upper Receiver
The Anderson Manufacturing Stripped Upper Receiver is a true stripped down upper receiver that is well made and the most affordable option on this list. Those on a tight budget would be hard pressed to avoid it.
See at Brownells

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Why Go With The .458 SOCOM?

The .458 SOCOM was designed for one specific purpose: to put down enemy soldiers quickly and with only one shot. In multiple combat missions throughout the globe, U.S. soldiers in SOCOM (Special Operations Command) units armed with standard issue 5.56x45mm NATO M16 rifles or M4 carbines were having to shoot enemy fighters multiple times to bring them down.

In 2000, it was decided that a more powerful cartridge should be developed that would offer significantly more stopping power than the 5.56. At the same time, the new cartridge would need to be fully compatible with the existing M4 5.56 platform. This means that existing magazines, springs, and buffers would need to be compatible with the new round. The new round also needed to be fully reliable in a semi-automatic and fully automatic rifle platform and be suppressor friendly.

In early 2001, the first .458 SOCOM AR rifles were developed. The .458 is a very short and plump 40mm cartridge that fits in standard 5.56 AR-15 magazines: a 30 round 5.56 AR magazine will hold ten .458 cartridges, and a 20 round AR magazine will hold seven. Of course you could also get magazines designed for the .458 SOCOM.

The .458 was adopted not only by SOCOM but also by other military units such as in the Coast Guard, who utilized the round in situations where heavier firepower than what the 5.56 offered was needed (such as to punch holes through boats). As with other military rounds, the .458 also filtered into the civilian market, where it quickly found advocates who touted its merits as a brush gun or for brown bear defense in Alaska.

As noted previously, the .458 has ballistics very similar to the .45-70 Government round. The .45-70 has been traditionally offered in single shot or lever action rifles, and is widely used by hunting guides in North America as protection against grizzly bears and other dangerous game animals. Once the .458 SOCOM arrived, it was as if one could fire a round nearly equivalent to the .45-70, but this time through the semi-automatic AR platform for a faster rate of fire.

For you, the .458 would be a great rifle to have for protection when out in bear country or even for traditional hunting. When used within moderate ranges of under four hundred yards or so, the .458 SOCOM can be used effectively to drop any big game in North America, including elk, moose, and brown bear.

In essence, if you own a traditional 5.56 AR-15 and are fully familiar with the platform, but would like to have an AR rifle chambered in a round that you can use for hunting the biggest game animals in North America, the .458 SOCOM is the round you’re looking for.

Buyer’s Guide To Finding The Best .458 SOCOM Upper Receiver


The .458 SOCOM is available across a wide variety of bullet weights and grains, from two hundred and fifty grains up to six hundred. This complicates things when searching for a .458 Upper Receiver, because there are some upper receivers that are only designed to handle the lighter bullet weights.

Assuming you want your .458 SOCOM rifle to handle the heavier rounds, you’re going to need an upper receiver that is strong and durable enough to do so.

Do you want to know what will happen if you buy an upper receiver that is not designed to handle heavier five to six hundred grain bullets? Simple: cases can get suck, locking lugs can break, and cracks could even develop in the upper receiver itself.

Keep in mind, even if you’re going to use the lighter weight two hundred and fifty grain .458 rounds, you would still need a more durable upper receiver than the kind you would get for a standard 5.56x45mm NATO or .308 Winchester receiver anyway.

This is why it’s vitally important for you to actually use an upper receiver designed for the .458 SOCOM round. Technically, you can use a 5.56 receiver for the .458 SOCOM so long as the ejection port has been opened up to be .620 inches wide and the barrel has been swapped out to accommodate the .458. But since not all 5.56 upper receivers will be able to handle the extra power of even the lighter bullet weights of the .458 over the long term, it will be wiser to just get a .458 upper receiver instead.

In essence, durability should always be a top priority with any AR receiver, but it’s extra important when it comes to the .458 SOCOM round.

Rust and Corrosion Resistance

One of the greatest enemies of gun metal in general is rust and corrosion. Whenever your firearm is exposed to moisture, whether it be from humidity, rain, or snow, it can rust if let unattended and uncared for.

AR rifles are no different, and to help mitigate the risk of rust and/or corrosion as much as possible, you would be wise to invest in an upper receiver that comes with a rust-resistant finish. Aluminum will often corrode when exposed to moisture for extended periods, but a hard coat anodized finish applied over that aluminum will help to prevent corrosion (as well as simply add more durability to the aluminum as well).


The .458 SOCOM is not designed to be an incredibly precise round at long distances (such as at or over a thousand yards). If that’s the kind of AR you want, you should be looking at a .308 Winchester or a 6.5 Grendel.

Nonetheless, you still want your .458 SOCOM rifle to be as accurate as possible at the longest ranges as possible, right? Even if you only plan on shooting within one hundred to two hundred yards, you don’t want your accuracy to suffer.

Parts Compatibility

You don’t just want an upper receiver that is durable enough to handle the raw power of the .458 SOCOM round. You also want an upper receiver that is compatible with the various other accessories you will need in order to create a better shooting experience.

For example, does the upper receiver have a rail attached to the top to add lasers or optics to the top? Does it have disconnect mounts to add lasers or sling attachment points to the side? One of the benefits to the AR platform in general is that it is a highly customizable platform, and you won’t want your .458 AR to be an exception.

Another reason you’ll want compatibility is to help reduce recoil. The .458 SOCOM is going to deliver a lot more kick than your 5.56 or .308 AR will, and if you don’t take action to reduce the recoil it’s going to simply not be as pleasant to shoot. Examples of things you can do in your .458 AR to reduce the recoil will be to install a muzzle brake and a recoil buffer spring, so you need to make sure that your upper receiver will be able to accommodate those things.

Finally, the .458 SOCOM was designed to be as compatible with the 5.56 AR as possible, an upper receiver designed for the .458 is supposed to fit on the lower receiver designed for a 5.56. If you already have a 5.56 lower receiver selected, it’s your responsibility to confirm that your .458 upper of choice will indeed fit over the lower. Theoretically, it should already fit, but you’ll just want to make sure.

The Top 3 Best .458 SOCOM Upper Receivers

Cross Machine Tool Co., Inc. AR-15/M16 .458 SOCOM Billet Upper Receiver

Cross Machine Tool Co., Inc. AR-15 M16 .458 SOCOM Billet Upper Receiver
The Cross Machine Tool Co., Inc. AR-15/M16 .458 SOCOM Billet Upper Receiver is constructed from a very durable T6 7075 aluminum with a hard coat anodized finish for superior durability and rust and corrosion resistance. This is incredibly important in order to handle the .458 round and to keep the rifle itself protected when you shoot it out in the rain or snow. Furthermore, the finish is a matte back color to help keep reflection from the sunlight to an absolute minimum to a non-issue.

This upper receiver is designed to accommodate not only the .458 SOCOM round itself, but also several other big bore AR calibers, and as a result it has an extended ejection port to reliably extract the larger-sized cartridges after each shot.

Cross Machine also ensured that this upper receiver would be fully compatible with standard AR-15 parts, and will accept standard 5.56 charging handles, bolt carriers, and barrel nuts; each of these parts are not included with the upper and will need to be purchased and installed by you separately.

The Cross Machine Billet Upper Receiver also lacks a dust cover and charging handle, although neither are necessary in order for it to function reliably. This is a very basic upper receiver that is affordable and a good choice for those who are relatively new to the AR platform.

If you’re looking for a basic, no-frills upper receiver for your .458 SOCOM AR, the Cross Machine Billet Upper Receiver is an excellent way to go. This is a durable and yet simple upper receiver that will get the job done and provides you with excellent overall value.

See at Brownells

  • Very Corrosion Resistant
  • Larger Ejection Port For Superior Reliability
  • Durable 7075 Billet Aluminum Construction with Hardcoat Anodized Finish
  • Excellent Value Overall
  • Fully Compatible with Standard AR Parts
  • Basic Option That Lacks Extra Features

Anderson Manufacturing .458 SOCOM Stripped Upper Receiver

Anderson Manufacturing .458 SOCOM Stripped Upper Receiver
If you want a .458 Upper Receiver that is even more bare bones than the Cross Machine Tool example just looked at, you’ll want to take a look at the Anderson Manufacturing .458 SOCOM Stripped Upper Receiver. This is a true stripped down upper receiver that is ready to be built from the ground up.

This means that first and foremost, this is an upper receiver meant for those who want to truly custom build their AR. Anderson Manufacturing has several upper receivers in their line-up, and several of their receivers are designed to be ready to go with very little custom work needed, but this is not one of them.  In other words, you need to be ready to put in the work if this is the upper receiver you buy.

That being said, if you are in the market to build a custom AR without spending a fortune, then this Anderson receiver is a great option. Built out of 7075 T6 forged aluminum, this upper receiver also has a hard coat anodized finish to make it more rust and corrosion resistance, and it has a matte black finish to help keep glare from the sunlight down to a minimum.

The ejection port is also wider in order to ensure proper extraction of the larger .458 cartridges, and the barrel extension has a larger relief for reliable feeding as well. A dust cover is not included with this receiver, but it will accept any standard sized dust covers and using standard pins.

If you’re looking to build a truly custom built .458 AR on a budget, the Anderson Manufacturing Stripped Upper Receiver is a good way to go. If you’re looking for a full package you will need to seek a receiver elsewhere, but those who get true enjoyment out of building their rifles will like the versatility that Anderson offers in this receiver.

See at Brownells

  • Wide Ejection Port
  • Durable 7075 T6 Forged Aluminum Build
  • Hard Coat Anodized Finish For Rust and Corrosion Resistance
  • Good Budget Option
  • Not The Best Choice For Those Who Don’t Want A Custom Build

Cross Machine Tool Co., Inc. AR-15 CMT Billet Upper Receiver .458 SOCOM

Cross Machine Tool Co., Inc. AR-15 CMT Billet Upper Receiver .458 SOCOM
The Cross Machine Tool CMT Billet Upper Receiver seeks to strike the balance between being a stripped upper receiver and a complete one. This means that this receiver comes with more features than the last two receivers that we’ve looked at today (such as M4-style feed ramps and a shell deflector), but not to the point that it can be considered a complete upper.

This is an incredibly durable upper receiver thanks to its T6 7075 forged aluminum build with a Type III hard coat anodized finish, which besides durability also creates excellent rust and corrosion resistance, and the ejection port has been enlarged to ensure proper ejection of the larger .458 and other big bore rounds.

Cross Machine also designed the CMT Billet Upper Receiver to be fully compatible with existing SOCOM Mil-Spec Parts, and the 5 Axis Machining Method that Cross Machine utilized for this upper receiver means that it should create greater accuracy for the .458 round than competing upper receivers (most upper receivers are built using a traditional 3 Axis or 4 Axis machining method).  As an added bonus, you’ll also get a lifetime warranty against manufacturer defects.

The CMT Billet Upper Receiver From Cross Machine is a very durable and well-made upper receiver designed to create the maximum performance for your .458 Upper Receiver. However, since it’s neither a fully stripped down or complete upper receiver, it neither allows complete customization or gives you everything you need right out of the box.

See at Brownells

  • Lifetime Warranty From the Manufacturer
  • Axis Machining Method Ensures Good Accuracy
  • Enlarged Ejection Port For Superior Reliability
  • Durable 7075 T6 Forged Aluminum Build
  • Type III Hard Coat Anodized Finish For Excellent Rust and Corrosion Resistance
  • Fully Compatible with SOCOM Mil-Spec Parts
  • Mixed Balance Between Stripped and Complete Upper, So Won’t Be Good For Those Looking For Either
  • More Expensive


The .458 SOCOM is a heavy round and requires a durable and quality upper receiver to handle it properly. Fortunately, investing in high quality parts will ensure that you get the best possible performance out of your custom .458 rifle.

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