Need the brain trust-

I have a Radical Firearms 10.5” setup that has about 100 rounds through it. I’m using standard GI issue mags and am having failure to properly feed and chamber about halfway through each mag. The pictures above show how the round is positioned during the malfunction. I’ve already dremmeled the front of the magazine as I’ve read that could be an issue. Down to looking at the feeding ramp. Any ideas or prior experience? Thanks in advance-

I throated my radical barrel to match a reliable well known 458 Socom brand.  Also check bolt face rough edges and bevel ejector. Mine feeds from GI 30 round unmodified mag with no issues.

Tromix sells 458 mags and followers.
458 Mags

This is one reason i returned my Radical 458 upper and went with Tromix.  I hope u do the same.

U can read my story here.  
https://www.ar15.com/forums/ar-15/458-Socom-failure-to-feed-/121-736578/

Your bolt probably looks like the one on the left.  Note the sharp edge around the top of the perimeter wall encircling the pocket.  That sharp edge digs into the case head and prevents it from sliding upward across the bolt face in order for the round to get parallel with the bore.

It doesn't matter if you're shooting an AR-15, Remington Model 700, 1911, whatever, the case head must slide smoothly up across the bolt/breach face or the round isn't going to feed.

The bolt on the left also has a 5.56 ejector in it, not a 458 ejector.  That certainly doesn't help.

Tony Rumore
Tromix

Edited to add: The feed ramp on the barrel extension is fine (Whitworth Tool Extension) but after the barrel is installed in the receiver, the ramp needs to be extended downward into the aluminum of the upper receiver if you want to feed blunt nose bullets.  Kinda like one big ass M4 feed ramp cut right in the middle.....then blended into the ramp on the extension.

Not true.  The .458 SOCOM was designed to work with standard unmodified GI mags from the get go.  It pretty much center feeds the .458 SOCOM.  Even with standard followers, the mag may hand stack slightly one side to the other but during actual life fire, they always feed from the center.   And I have never had a problem dropping the bolt on a round with it to one side or the other in the magazine and had a fail to feed.  I have a dozen .458 SOCOMS from 6.750 to 28 inches and have used just about every type of quality magazine out there, and the only mag that has ever given me trouble are P-Mags with spitzer bullets because of that front rib.  I've never had to modify feed lips or even cut the half moon in the front, although I do cut the half moon to make unloading unfired rounds easier.  I have never encountered a need for them to be there for feeding.

You don't need to do anything to decent 5.56 mags to make them feed in a properly built upper, which Radical are well known NOT to be.  From the looks of those pictures, the jam is being caused by what Tony said, the unmodified ejector.  You must have that bevel he showed in his picture so the case head can enter the bolt face.
I tried one non TROMIX .458 SOCOM bolt, a complete BCG sold as Tool Craft from Joe Bobs, and it could not be made to feed the .458 SOCOM round no matter what.  Three problems, ejector not beveled, extractor not modified correctly, and bolt face too small.  Good thing I bought it on sale and only need the BC and guts, not the bolt, because the bolt was a POS.  After replacing the extractor with a TROMIX, modifying the ejector, and getting Paladin to open up the bolt face to spec, it works now, but the bolt Joe Bob used in their .458 SOCOM Tool Craft BCG is complete garbage.

OST