FAQs
Frequently Asked Questions
Generally speaking, you want to avoid using any goofy/Gucci 5.56 upgrade parts on your 458 SOCOM upper. The Tromix uppers are designed and built to run with standard GI type parts.
Q: Which 458 SOCOM parts are different from 5.56 parts?
A: The only unique parts to the 458 SOCOM uppers are the barrel, bolt, upper receiver, and muzzle attachment.
Q: Do I need a heavier buffer or spring in my lower?
A: No. The gas port is sized to blow the bolt carrier completely rearward with a standard GI buffer and spring. Adding a heavier buffer or spring may cause the bolt to short stroke.
Q: Do I need a heavier extractor spring or insert?
A: No. Too much extractor tension will cause pieces of brass to be chipped off the rim of the case.
Q: Do I need an adjustable gas block?
A: You only need an adjustable gas block if you are shooting full power supersonic ammo, suppressed. You don’t need an adjustable gas block for shooting subsonic suppressed, subsonic unsuppressed or supersonic unsuppressed.
Q: What is the velocity loss when going to a shorter barrel?
A: Velocity will drop 25 feet per second per inch down to 10.5″, then will drop 50fps per inch below 10.5″.
Q: Where can I get load data for the 458 SOCOM?
A: Pressure tested load data is available in Western Powders, Nosler, Sierra, Hodgdon and Lyman load manuals.
Q: What magazines should I use with my .458 SOCOM upper?
A: All 5.56 magazines will work with the .458 SOCOM other than Magpul P-Mags. Those have a center divider in the front that can block the bullet path. It appears that Lancer has inadvertently made a change to the feed lips on magazines date coded 2021 and newer. 2020 and earlier magazines feed fine.
Q: What is the warranty on Tromix parts?
A: If you act like a reasonable adult, there is an unlimited warranty on all parts. However, if you act like an asshole, there is no warranty.
Q: I’m having feeding problems with my Tromix barrel. Do I need to pull out the Dremel and destroy the barrel extension?
A: Put down the tools and step away from the bench. There is nothing wrong with the barrel or extension. If you are having feeding trouble, it’s an issue with your bolt, and you most likely didn’t buy the bolt from Tromix.
Q: Do I need a left handed barrel/extension to go with my left handed receiver?
A: No. All of our barrels will work in either right or left hand configurations.
Q: I got a great deal on a cheap 458 SOCOM upper (not Tromix), but it’s having feeding problems. What may be causing that issue.
A: 90% of feeding issues with the 458 SOCOM are attributable to an incorrectly machined bolt.
Q: I got a great deal on a cheap 458 SOCOM upper (not Tromix), but it’s having random failures to eject.
A: Many manufacturers of large bore upper receivers only raise the ejection port at the front half of the opening, and leave the rear portion in the same position as a 5.56 upper. This can cause random failures to eject since the casing is usually ejected at the rear portion of the port.
Q: Using the ARFCOM ejection pattern protractor, my upper is ejecting forward, around 1 – 2 O’clock. Is that indicative of a problem?
A. No. The .458 casing has a rebated rim which causes the bottom of the case body to strike the nose of the extractor as it rolls out. This causes the case to be ejected more forward than that of non-rebated rim cases.
Q: I loaded some ammo using new Starline brass and it won’t chamber in my Tromix upper.
A: All new 458 SOCOM brass needs to be resized prior to loading. The shoulder position on new Starline brass is not always in the correct location for proper head space. Many times the shoulder is a bit too far forward on the case and needs to be pushed back a hair. We recommend purchasing a Tromix cartridge gauge in order to set your sizing die correctly.
Q: I loaded some ammo which fits perfectly in the Tromix case gauge but won’t chamber in my Tromix upper.
A: Per the instructions that came with the Tromix case gauge, the loaded cartridge needs to drop BELOW flush with the top of the gauge. If the cartridge case head sits flush with the top of the gauge, your ammo is out-of-spec. We recommend the case head drop .003-.005 below the top of the gauge.