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Posted: 9/18/2026 2:21:15 PM EDT
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Does .375 SOCOM require the barrel extension feed ramps to be paired with an upper receiver with NO M4 feed ramps, similar to .458 SOCOM? If so, does your .375 SOCOM 16" complete upper have blended/polished feed ramps? I assembled my own .458 SOCOM and have troubleshot it to the point where it seems a barrel extension/chamber blending/jobis required but that is beyond my skill level. I figured that the smaller diameter of the .375 would feed better in the AR15 platform than the wide, blunt .458 bullet. Please let me know your recommendations. |
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All my .375S have blended feed ramps so IMO it should be done. But, the bottleneck case may make blending less necessary but if the barrel extension feed ramp has a shelf below the ramp, it’s probably best to blend. Blending the feed ramp to the barrel extension is not rocket surgery. A Dremel and a fine chainsaw sharpening stone and you can blend the upper to the feed ramp quite easily. Then follow up with a rubber tipped bullet shaped polishing bit and you are done. If you freak out over the bare aluminum, hit it with Aluma-Black and quit worrying about nothing. Who made your problematic.458 barrel and bolt? My guess is it’s not a TROMIX. |
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Thank you for sharing your first hand experience, that assuages my concerns that any blending that is actually required is not a catastrophic project. My .458 SOCOM barrel and bolt are from KAK, not a headspaced pair. Magazines are D&H with the half-moon cutout at the front wall, ammo is 350gr FMJ flat point. It cycles appropriately about 40% of the time after 60 rounds being fired through it. The cartridge tends to have a falure to feed by binding on the top center point of the barrel extension/chamber face. The magazines have about a 90% success rate for feeding after trying Duramags initially but still some get stock on the bottom center of the barrel extenstion area. Another forum reply recommended polishing/light blending of the top extension/chamber face to aid with the stovepipe/type feed error. I am considering that the time/effort/cost of tools and test ammo at this point may be more economic to buy a headspaced .375 SOCOM barrel and bolt from Tromix/Southern Ballistic Research and have a much greater degree of certainty. |
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Can you post a picture of the feed ramp? if not done correctly, that can be the issue. As Big Bore noted, you can fix that yourself with the trusty rotary tool. Also, if the bolt has not been given the proper attention - particularly the extractor and ejector - that can cause issues. A picture of the bolt showing those two can also help us see if there could be a tweak to be done there. And if they were overly aggressive on opening the bolt face, leaving the remaining edge too thin, that can sometimes give some headaches as well. We'll get you sorted. |
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