Click on a Frequently Question Below to Link to the Answer.

  1. Who developed the .458 SOCOM? Was it Tromix?
  2. Can I form my own cases? Isn?t it just a necked .50AE?
  3. What does SOCOM stand for?
  4. Where can I buy an upper or suupressor?
  5. You mentioned the .50 BeowulfTM. Which is better, the .458 SOCOM or the .50 BeowulfTM?
  6. What is the best twist rate?
  7. What is the optimum barrel length?
  8. What is the shortest possible barrel?
  9. What type of velocity can I expect?
  10. What type of accuracy can I expect?
  11. What is the maximum range I can use the .458 SOCOM?
  12. What kind of recoil can I expect?
  13. What lower, stock, other parts can I use?
  14. What are the best or preferred optics?
  15. Where can I buy loaded ammo?
  16. Can I shoot subsonic loads?
  17. How loud are the subsonic loads?
  18. What about putting a suppressor on one of these?
  19. Do I need a muzzle brake? Do you offer one? What about flash hiders?
  20. What about reloading?
  21. I am new to reloading, would this be a good cartridge to learn on?
  22. Where do I get brass, bullets, etc.?
  23. What is the trim length for the brass?
  24. How do I resize the brass?
  25. What bullets can I use?
  26. What about crimping? Bullet set back?
  27. What primers should I use?
  28. What powders should I use?
  29. Where do I get dies?
  30. Where can I find load data?


  Who developed the .458 SOCOM? Was it Tromix?

The .458 SOCOM was developed by Marty ter Weeme, founder of Teppo Jutsu LLC in 2000. The impetus was an informal ("beer and barbeque") discussion with a senior member of the US special operations community regarding the apparent lack of effectiveness of the 5.56 x 45 cartridge in recent conflict. In particular, the reports from members of Task Force Ranger in Mogadishu, Somalia that multiple shots were required to neutralize members of the opposing force led to the request to develop a new cartridge that would deliver far more energy from short barrels at relatively short distances. After the design was completed, Tony Rumore of Tromix Corp in Broken Arrow, OK was contacted to build the first prototype. Based on the favorable reviews, commercial production was started and the initial rifles were produced by Tromix. Buddy Singleton from Southern Ballistic Research, LLC (SBR) in Brunswick, GA was asked to developed factory loaded ammunition for the 458 SOCOM. Today, they are the leading manufacturer or factory loaded 458 SOCOM, and they continue the R&D on the cartridge.


Can I form my own cases? Isn?t it just a necked .50AE?

You could form your own brass; however it would be economically unwise. The only case that has the proper base diameter and rim diameter is the .425 Wesley Richards, which runs about $4 a piece. Any other brass will not have the proper rim size, either too large or too small. In a pinch, you could form .458 SOCOM from .50 BeowulfTM but the rim would be smaller. The initial prototype brass bore the .50AE head stamp and this has caused some confusion. The SOCOM case is 1.575" long, the .50AE is 1.290" so therefore, you CANNOT form the SOCOM case from the AE case.


What does SOCOM stand for?

SOCOM refers to Special Operations COMmand, the joint service command based in McDill, FL that governs the various special operations units such as Naval Special Warfare ("SEALs"), Army Special Forces ("Green Berets") and Air Force Special Operations. The cartridge was given this name based on the original impetus from special operations mentioned above as well as the fact that a similar cartridge saw limited use in Vietnam with special operations as well.


Where can I buy an upper or suppressor?

There are a number of companies producing uppers and suppressors. These are a few below

SBR: (uppers, suppressor, complete rifles)www.SBRammunition.com

Tromix Corp (uppers) www.tromix.com

Rock River Arms (uppers and complete rifles) www.rockriverarms.com

In addition, there are a number of other companies that supply uppers; however, but may lack the experience in the 458 SOCOM. The 458 SOCOM is not like building a standard 5.56mm upper.


You mentioned the .50 BeowulfTM. Which is better, the .458 SOCOM or the .50 BeowulfTM?

This is one of those debates that neither side wins. Both cartridges are very similar, yet they are quite different. We had access to some of the information on the predecessor of the .50 BeowulfTM when we designed the .458 SOCOM. We designed it the way we did for very specific reasons. I admit I cannot be impartial, but I will give as honest a comparison of the two as I can:


Rim size ? the SOCOM rim is the same as the .308 Winchester (7.62 x 51), the Beowulf rim is the same as the 7.62 x 39 M43 cartridge used in the AK-47. The B rim is easier in that you can use existing bolts for the AR. The S rim is easier in that there are hundreds of thousands of (old) bolt action rifles that use this same rim and that could be retrofitted to the SOCOM (all the old Mauser rifles ?.)

Case length ? as mentioned earlier, the B is 4mm longer than the S. A lot of this extra room is taken up by the body of the bullet anyway, so it does not gain you that much.

Headspace ? the B uses the case mouth, the 458 SOCOM the shoulder. There are those that feel using the shoulder offers inherent greater accuracy potential, but both rounds are capable of just about the same accuracy. Both are intended to be used at the same maximum range as well, so it really does not matter much.

Bullet selection ? this is where the S has the B beat, hands down, due to large variety of .458 bullets compared to the .500. But with the advent of the .500 S&W, the B is starting to catch up.

Cost/Selection ? Before Rock River got into the game, the 458 SOCOM uppers were all custom jobs whereas the B uppers were more "semi-bulk". The 458 SOCOM uppers are available in just about any configuration you can imagine. The B uppers come in a certain number of configurations as well.

Power ? Let?s be honest. The difference between a .458" bullet and a .500" bullet is a whopping 0.042" or a hair under 3/64". If you hit anything with either, it will be hurting or dead. That 0.042" won?t matter a bit. Both have just about the same muzzle velocity so just about the same power. The B has a little more room for powder and with the slightly larger diameter bullet will edge out the 458 SOCOM. But the S has bullets with much better BC available so it should out perform the B at distance.

So as you can see, the difference is really not that big. A lot of it depends on personal preferences, or perhaps what your budget is or whether you already reload or similar considerations. You can?t go wrong with either.


What is the best twist rate?

One of the reasons .458 was chosen was to allow the use of the commercially available heavy bullets (500 and 600 grains). To stabilize these at subsonic velocities, a relatively fast twist is needed. If you plan on shooting mostly light bullets (250-400) you can get away with slightly slower twist and the slower twist MAY stabilize the 600-grain bullets but likely won't. Basically the 1:14" twist is standard


What is the optimum barrel length?

The cartridge is intended as a short range "brush buster". As such, we feel the optimal length is about 16", as a compromise between handling and velocity. Longer barrels will NOT offer substantially more velocity due to the fact that relatively little powder is available and relatively fast burning powders are used. As a matter of fact, the factory loaded 600-grain subsonic load is designed to achieve complete powder burn in a 9.5" barrel. Most of the uppers that have been built have featured 16" barrels, with the second most popular length being 20", followed by 10.5" for SBRs/pistols.


What is the shortest possible barrel?

The typical short barrel upper will have a 10.5" barrel; however we have managed to make an upper function with a 7.5" barrel. You can't go much shorter than that.


What type of velocity can I expect?

Velocity will vary from rifle to rifle and obviously also depend on the bullet that is being loaded. However, some of the typical velocities from a 16" barreled upper are as follows:

300 grain bullet ? 1800 to 2000 fps

400 grain bullet ? 1600 to 1800 fps

500 grain bullet ? 980 to 1300 fps

600 grain bullet ? 1000 fps

What type of accuracy can I expect?

As with velocity, accuracy will vary from rifle to rifle. The cartridge, however, is capable of quite respectable accuracy. With hand loads, low power optics and the shooter doing his job, groups as low as 0.5" (yes, true 0.5") have been recorded. We typically tell folks that 1.0" groups at 100 yards are the norm for the 300-grain JHP load. The 550-grain FMJ from SBR Ammunition load is shootting under 1 MOA at 100 yards from their 16" 1:14" barrel.


What is the maximum range I can use the .458 SOCOM?

The cartridge was intended for short range work, either in dense brush or otherwise in urban theaters for LEO/MIL applications. As such, after 125-150 yards, the bullets tend to drop off VERY rapidly and we tell folks to consider it a 100-150 yard cartridge. Accomplished shooters can shoot the cartridge accurately at much greater distances, just like the .45-70 was used to decimate the American bison population at 1000 yards.


What kind of recoil can I expect?

Recoil is subjective, however, most of the folks who have shot it tend to use the comparison to either a 20- or 12-gauge shot gun. The 400-grain loads seem to have the most unpleasant recoil impulse, the 300-grain does not appear that bad nor does the 500- and 600-grain subsonic load. I have shot it in a 10.5" SBR on full auto with 300-gr. JHP loads and found it not that hard to handle. From the bench my .308 has seemed to kick worse. See the next section about some pointers. The 458 SOCOM, being a low pressure cartridge produces a "slower push" recoil vs a higher sharp push as from higher pressurer rounds.


What lower, stock, other parts can I use?

The .458 SOCOM was designed to fit any mil-spec lower. Thus, any of the lowers out there that meet mil-spec should readily accept the .458. No modifications should be needed to your lower and no negative effects to the lowers have been reported.

Barrel ? SBR has barrels available made to the original Teppo Jutsu specifications. www.SBRammuniton.com

AR15 Bolt ? Beware of AR15 bolts that have been cut from 5.56mm bolt. Turing a 5.56mm bolt to make a 458 SOCOM weakens the surface hardness. Must used bolts that are original made to the 458 SOCOM specifications. SBR has AR15 458 SOCOM bolts. www.SBRammuniton.com

Stock ? Any mil-spec stock that is confortable for you.

Buffer Spring ? While the standard spring will work, some shooters prefer a spring with higher spring constant.

Buffer ? Again, the standard buffer will work.

Magazines ? the .458 SOCOM was designed to work with any GI/Mil Spec magazine. We have not heard of any particular type or brand of magazine that did not function. Magazine capacities for the different size magazines are as follows:

10 rounds of .223 ? 3 rounds of .458 SOCOM

20 rounds of .223 ? 7 rounds of .458 SOCOM

30 rounds of .223 ? 10 rounds of .458 SOCOM (have heard 12)

40 rounds of .223 ? 13 rounds of .458 SOCOM (have heard 15)

The MWG 90-round .223 drum can hold as many as 33-36 rounds of .458 SOCOM which makes for some formidable firepower. The BETA mag WILL NOT WORK with the SOCOM.


What are the best or preferred optics?

Which is better, Ford, Chevy or Dodge? Because of the recoil, the preferred optic will have longer eye relief than typical. Lower power scopes such as those originally intended for use with a shotgun are popular, however, the vast majority of shooters use either the Aim Point or the EOTech as these seem particularly well suited to the type of shooting done with the .458 SOCOM.


Where can I buy loaded ammo?

There are a number of small ammunition manufacturers loading the 458 SOCOM.  However, SBR is the largest producer of factory ammunition for the 458 SOCOM, and they offer the widest selection. They are one of the original.  Being a SAAMI member, they pressure test all factory developed loads. They are continuing the R&D process, and hope to have the 458 SOCOM adopted by SAAMI in the near future.


Can I shoot subsonic loads?

Considering this was part of the original design intent, the answer is a resounding YES. Both the 500- and 550-grain subsonic load has proven quite popular and will function without issue through the uppers.


How loud are the subsonic loads?

While not as loud as the 300-gr high velocity load, they are still not quiet enough to forego ear protection.


What about putting a suppressor on one of these?

Several uppers have been fitted with suppressors, either muzzle mounted or semi-integral versions. With the 500- and 550-grain subsonic load they tend to make for a very nice and relatively quiet package. Suppressing a low pressure large bore cartridge has its challenges, and Hollywood has created a false impression of how quiet a suppressed rifle typically will be. These uppers are not like you see in the movies and a lot of the noise is from the action cycling. If you want the ultimate in suppressed .458 SOCOM, the Remington 700 Etronix version with semi-integral suppressor would have to be it. Other calibers are far more suited to suppressing but the SOCOM is no slouch. Remember that the 11.63 x 33 was used in suppressed bolt guns in Vietnam ?. SBR offers a variety of suppressor models for the 458 SOCOM that perform nicely.



Do I need a muzzle brake? Do you offer one? What about flash hiders?

This depends on how recoil sensitive you are. ANY benefit in terms of recoil will come at the cost of increased noise to the shooter and surroundings. Because of the large bore and relatively low pressure, most muzzle brakes will not be quite as effective with the .458 SOCOM as they might be with a cartridge like the .22-250. SBR Ammunition does offer different versions and some folks report that they make a tremendous difference. A lot of it depends on the shooters preference. If you are building your own rifle and have a barrel with 5/8-24" threads, besure to check the hole diameter of the muzzle device


What about reloading?

Reloading can save you some cost in shooting the 458 SOCOM. New, Factory made ammo has that added Federal Excise Tax of 11%. That $50 a box of 458 SOCOM, $5.50 goes to good old Uncle Sam. There are a lot of 0.458 dia bullets available, not all are suited for the 458 SOCOM. This is due to the case overall length and the throat length limited within the AR15. Loading dies are available from Lee, Redding, Hornady, CH, etc. Contact SBR Ammunition for help with loading data. info@SBR-USA.com


I am new to reloading, would this be a good cartridge to learn on?

To be honest, the SOCOM can be a finicky round to load compared to such rounds as the .30-06, the .45-70 and many others. It would probably not be the best one to learn on, as it has a few idiosyncrasies, but if you like a challenge?.


Where do I get brass, bullets, etc.?

The brass is made by Starline and SBR and can be bought straight from them or else through the larger reloading specialty outlets like Midway and Graff and Sons. Just about ANY of the .458 diameter bullets out there will work, and these are readily available at most gun stores that offer reloading components. SBR Ammunition sells their lower cost FMJ bullets.


What is the trim length for the brass?

The official length is 1.575" but you can go as "short" as 1.570".


How do I resize the brass?

More important than trim length is shoulder set back as this cartridge head spaces on the shoulder. Experienced reloaders will know what this means, but for those that do not ? you have to set up your dies such that when you full length size the brass after firing, you do not push the shoulder back down the case. If you were to do so, the case would still chamber, but likely FAIL upon firing. Not a huge issue, just a pain. I have had several do this, before I got my dies dialed in properly. Sometimes the shell holder can make al the difference needed ?. I run my dies all the way down to where the fully contact the shell holder and this works for me but again; there are variances in shell holder thickness which can cause problems.


What bullets can I use?

As stated above, just about any .458 diameter bullet, ranging from 250 grains to 600 grains is what we have found out there. Cast lead could be used, but we would recommend limiting the number of cast lead bullets as the lead may foul the gas system. Seating depth can be a bit of a challenge with some of the heavier bullets. NOTE that the crimping groove on many .458 caliber bullets was designed with a totally different cartridge in mind (typically .45-70 or .458 Win Mag). Therefore, the crimping groove will likely NOT line up with the case mouth when seating to an overall length that fits in the magazine (or chambers, there are some bullets that need to be seated deeper due to their profile, such as the 300-grain SinterFire frangible and the 400-grain Speer FN)


What about crimping? Bullet set back?

Crimping is a topic of quite some debate. Both the CH dies and Lee dies allow you to crimp. Typically crimping is recommended to prevent set back of the bullet due to recoil or during the feeding process. However, several shooters report no issue when not crimping and one accomplished reloader/shooter reported a decline in accuracy when crimping. I tend to put a light crimp on my loaded rounds with my CH dies and have not encountered an issue ? yet.


What primers should I use?

The cartridge case uses the large pistol primer pocket and we recommend the CCI #300 or the WLP primers to start.. Some powders do perform better with magnum primers, CCI #350. DO NOT use rifle primers as the primer pocket is not deep enough to seat them property which could lead to a very dangerous situation.


What powders should I use?

With a relatively small powder volume and low pressure, the faster rifle powders tend to be the more popular and effective. Typical powders include Hodgdon H110, Winchester Win296, Norma N200, Alliant Reloder7, IMR4198, SBR-SOCOM, and VVN110. Contact SBR Ammunition for help with loading data. SBR Ammunition now offers their OEM powder in 1 lb and 8 lb containers. www.SBRammuniton.com


Where do I get dies?

Loading dies are available at many locations that sell reloading equipment. Lee, Redding, Hornady, and CH have 458 SOCOM dies.


Where can I find load data?

Right now, the best place is to Email SBR Ammunitiinon. info@SBR-USA.com

If you are handloading the 458 SOCOM, a Case / chamber gauge is a must have. This allows you to check your sized brass and completed load round to ensure in meets size specifications. The 458 SOCOM is a large surface area cartridge and can fall out of specification if not properly loaded. In an AR15, the barrel extension blocks your view of the chamber, the first indication of an out of spec round is your bolt jamming and locking closed. SBR worked with L.E. Wilson to custom produce gages to original specifications. If your round fits in this gage, it will fit in a correctly chambered 458 SOCOM barrel or rifle. These gages serve as the "standard" while SBR and us continue to work on getting the 458 SOCOM adopted by SAAMI.

SBR 458 SOCOM Gages



I think this covers just about everything, if I missed anything let me know


Marty ter Weeme
Founder, Teppo Jutsu LLC

Developer of the .458 SOCOM


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