Anderson Manufacturing .458 SOCOM Stripped AR-15 Upper Receiver

Manufactured by Anderson Manufacturing
SKU: D2-K100-458
MPN: D2-K100-458
Manufactured by Anderson Manufacturing
9 Reviews

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The Anderson Manufacturing .458 SOCOM Stripped Upper Receiver is built to Mil-Spec for compatibility with most forged AR-15 lower receivers. It is constructed from a 7075-T6 aluminum forging and machined with M4 feed ramps to aid in reliability when chambering. The .458 SOCOM upper also features an extended and widened ejection port for proper ejection of larger cartridges. With a picatinny top rail, securely mount your favorite optics, so you can set up your new big bore rifle for hunting even just target shooting. This stripped upper receiver from Anderson Mfg. has all the features you need when building a .458 SOCOM AR-15 at an affordable price.

NOTE: Forward assist and ejection port cover sold separately.

  • Oversized ejection port for .458 SOCOM
  • 7075-T6 aluminum
  • M4 feed ramps
  • MIL-SPEC Type III hardcoat anodized black
  • Picatinny top rail
  • Compatible with Mil-Spec AR-15 lower receivers

This stripped upper receiver is designed to be as compatible with Mil-Spec AR-15 parts as possible. Standard charging handle, forward assist, and even barrel extensions are the same. All you need is a .458 BCG, enlarged ejection port cover, and .458 barrel and you are ready to build your upper receiver. It even works on standard AR-15 lower receivers with standard parts, so you can have one lower receiver and multiple uppers chambered in different calibers and swap them out when you want.

Anderson Manufacturing builds rifles, pistols, and parts utilizing the latest in computerized manufacturing. By keeping manufacturing in house, Anderson can offer quality, American-made products at an affordable price, backed by a limited lifetime warranty.
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BrandAnderson Manufacturing
Feed RampsM4
FinishHardcoat Anodized
Forward AssistAccepts Standard Forward Assist
Port DoorAccepts Standard Port Cover
Receiver Material7075-T6 Aluminum
T MarksUnmarked
Weight6.56 Oz
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to

Ratings & Reviews

9 reviews

  • 4 stars
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One star for one shot.

by -

So I guess I'm first here. Well no need to be second since the "Oversized ejection port for .458 SOCOM" doesn't even fit a casing through it.
I guess if you want a single shot it works, but there are better options out there.

May just be the Magazine???


I do not have one of these, but I have a friend that does. This is just additional information that may or may not help. The problem my friend ran into is in the magazines that are available. They must be single stack and modified to handle this round. I'm not sure what he did....I wish I had paid more attention. I never thought about owning a 458 SOCOM until I got to shoot his. Just saying.

Awesome stripped upper

by -

I ordered this on special sale even though the one review was really negative. I have used Anderson for a lot of builds and never had a problem. The first thing I did was to check the ejection port opening. I have a 450 Bushmaster so I took a round and it fell through with plenty to spare. I received everything today at 1 pm for my 458 socom build, at 6 pm ready to shoot. Now I need to order ammo! Primary shipped so fast it cought by surprise. Maybe the other reviewer was sent a standard upper by mistake. I would tell him to reorder, this thing is awesome. Thanks Primary will add you to my go to vender list😊

Perfect upper

by -

I ordered this 458 Socom stripped upper on sale. I read the one review that said the ejection port would not fit a casing through. When I received mine I hadn’t built my upper yet, so I didn’t have any 458 to try. I do have a 450 Bushmaster and those rounds cleared with room to spare. I have now completed my build and rifle functions perfectly. Thanks Primary for your fast shipping and customer service!

This upper is a definate must for your big bore AR build.

by -

Decided to build a 458 Socom, I chose this upper along with the PA barrel, BCG, freefloat grip, and an upper kit it assembled very nicely. I was apprehensive due to the one negative review.... not now. There were some tweaks needed to the barrel and the BCG along with an H3 buffer but then it just wanted to be fed …. this upper worked as it should... will buy again --- got the urge to do a 450 Bushmaster too.

Good to Go.

by -

I have built a lot of .458 SOCOMs and wildcats based on the .458 SOCOM so this is not my first rodeo. I usually have my uppers modified by my smith but seeing this upper already modified for less than $50, what the heck, I'd give it a try. The ejection port is just fine so I can only assume the other guy got a standard upper and did not both to follow up with calling PA to get it sorted out. Nobody can fix a problem for which they are not made aware.

The forward assist installed easily, no problem, and the front of the receiver squared up nicely with only a little lapping needed to square it off perfectly. The ejection port cover snaps shut with authority so they did not muck it up by removing too much from the top of the ejection port, as I have seen others do and there is plenty of clearance for the .458 S case to eject unimpeded. I have not experienced any problem with it at all and will order another as the need arises.

Not big enough for .50 Beowulf

by -

Does not work for 50 beowulf.

From PA: These are not designed to work with .50 Beowulf. These uppers are designed for .458 SOCOM.

No Problems Here


I've built four 458 SOCOM carbines using Anderson 458 stripped upper receivers. I still use one for deer & hog hunting, and the other three are used by son, and two grandsons. All told we have between 200 and 300 rounds thru the four. Two are on Anderson lowers, one on a Bushmaster, and one on a Palmento State Armory lower receiver. We use 20 round mags with a caliber specific 458 follower bought from a guy in Iowa thru flea bay. We have never had any issues with any of the 458 Anderson stripped uppers we own. If Carl can't get a 458 she'll thru the ejection port, I would bet $10 bill he got a regular 223/5.56 stripped upper. One should always check clearance prior to assembly. I've used Anderson stripped uppers and lowers to build several 5.56 and 7.62x39 carbines, and only have good things to say about their products.

another great anderson mfg product

by -

The description is wrong - this upper receiver does not have the M4 feed ramp extensions cut into it which is a good thing if you are building a 350 Legend or a CMMG 9mm RDB upper with it