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Frequently Asked Questions

Generally speaking, you want to avoid using any goofy 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: For non-suppressed shooting, you don't need an adjustable gas block.  For shooting both suppressed and unsuppressed, an adjustable gas block is recommended.

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, 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.  We recommend Lancer magazines for the best feeding reliability.

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.

Return, Exchange and Privacy Policy


Return & Refund Policy

Thanks for shopping at If you are not entirely satisfied with your purchase, we're here to help. 

Returns/Exchanges: You have 10 calendar days to return an item from the date you received it. To be eligible for a return, your item must be unused, unfired and in the same condition that you received it. Your item needs to have the a copy of the receipt, along with an explanation on how to proceed i/e Return, Exchange, Refund.

Once we receive your item, we will inspect it and notify you that we have received your returned item. If your return is approved, we will initiate a refund to your credit card (or original method of payment). You will receive the credit within 2-7 business days, depending on your card issuer's policies. 

Return/Exchange Shipping: You will be responsible for paying the shipping costs for returning your item, unless it was due an error on part.  Shipping costs are nonrefundable. If you receive a refund, the cost of return shipping will be deducted from your refund.


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