458 Socom BCG "sticks"

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  • clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    O.P.

    Remember you need to remove the extractor and ejector to get a proper reading with H S. Gauges.

    The previous poster is correct about .458 and saami specs. It's another caliber that suffers uniformity because of petty industry B.S. Ammo can be the problem but there is no reason why the gun can't be corrected to work on all commercial loads safely.

    If the shoulder's in the wrong place that will make it a headspace issue. Without a reamer, which is almost impossible to get outside PTG. Lapping the lugs would be the next step to get it to chamber the ammo you are dealing with, but that has to be done with a bolt tensioner and H.S. gauges.

    Personally I would just mandate the manufacturer refund your money and get away from this caliber.
     

    RetiredArmyGuy

    Active Member
    Jan 16, 2018
    171
    Pasadena, MD
    O.P.

    Remember you need to remove the extractor and ejector to get a proper reading with H S. Gauges.

    The previous poster is correct about .458 and saami specs. It's another caliber that suffers uniformity because of petty industry B.S. Ammo can be the problem but there is no reason why the gun can't be corrected to work on all commercial loads safely.

    If the shoulder's in the wrong place that will make it a headspace issue. Without a reamer, which is almost impossible to get outside PTG. Lapping the lugs would be the next step to get it to chamber the ammo you are dealing with, but that has to be done with a bolt tensioner and H.S. gauges.

    Personally I would just mandate the manufacturer refund your money and get away from this caliber.

    If we where speaking about any other caliber I would agree with you. But in this case the difference between the RRA/Tromix/SBR reamer and the reverse engineered reamer by PTG/Wilson is what causes the issue. RRA cuts their chambers extremely tight which causes problems with non SBR ammunition.

    I manufactured 458 SOCOM ARs for 4 years using Tromix barrels which are IMO the best barrels to use if you want to shoot this caliber. The one thing I have always told people about this caliber is if you are going to own it you really need to roll your own ammunition. Since there is no SAAMI for this caliber “commercial” manufacturers like Underwood set their own specs which often times don’t work properly in all 458 Socom chambers. I would bet money that the Underwood ammunition will not fit in the case gauge I have which is a Tromix case gauge cut to the original Tepo Jetsu chamber specs for this caliber.

    Prior to manufacturing these rifles I purchased an RRA upper to do some testing. It was doing the same thing the OP described when I was using “commercial” ammunition but not from SBR. I sent it back to RRA and built and upper using Tromix parts. Haven’t had a problem with a Tromix barrel yet as long as the cartridge will fit in the case gauge.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    Perhaps i got lucky w/ my upper. after cleaning the gunk off the BCG AND having a dedicated magazine; it's no longer posing a problem. this weekend i shot 30 rounds. Shoot one, use charging handle to clear round, reload repeat. No issues so i shot at some milk jugs... nasty stuff right there.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    thanks for all the help and info in this process guys/gals. means a lot, really it does.
     

    RetiredArmyGuy

    Active Member
    Jan 16, 2018
    171
    Pasadena, MD
    thanks for all the help and info in this process guys/gals. means a lot, really it does.

    I would still recommend that you order a case gauge from Tromix even if you are only shooting commercial ammunition. If the cartridge will fit in the tromix case gauge it will fit in your chamber. Also if you reload and want some load data for the cartridge let me know. I have spent a lot of time and effort over the last few years loading and shooting this cartridge. It is an extremely fun and powerful cartridge to shoot. The attached picture is one of a couple of 458 SOCOMs I own.
     

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    jrumann59

    DILLIGAF
    MDS Supporter
    Feb 17, 2011
    14,024
    Perhaps i got lucky w/ my upper. after cleaning the gunk off the BCG AND having a dedicated magazine; it's no longer posing a problem. this weekend i shot 30 rounds. Shoot one, use charging handle to clear round, reload repeat. No issues so i shot at some milk jugs... nasty stuff right there.


    So was the problem the gunk on the BCG or the old mag?
     

    SWO Daddy

    Ultimate Member
    Jun 18, 2011
    2,468
    Tangent - does this round need a stronger receiver? I think I read that CMMG uses a beefier lower for their 458.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Tangent - does this round need a stronger receiver? I think I read that CMMG uses a beefier lower for their 458.
    CMMG has a line of rifles that are about halfway between AR-15 and AR-308. I don't think it's necessary for 458 SOCOM, but it does let them put in a much beefier bolt.

    Sent from my ZTE A2017U using Tapatalk
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,564
    Harford County, Maryland
    CMMG has a line of rifles that are about halfway between AR-15 and AR-308. I don't think it's necessary for 458 SOCOM, but it does let them put in a much beefier bolt.

    Sent from my ZTE A2017U using Tapatalk

    Are you referring to strength and mass or is that also an intermediate action length relative to the AR15 and AR10 actions?
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Are you referring to strength and mass or is that also an intermediate action length relative to the AR15 and AR10 actions?
    Intermediate receiver size. I'm not really the guy to tell you the precise differences, but if you look at CMMG Mutant reviews, those will cover quite a few.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    So was the problem the gunk on the BCG or the old mag?

    i should try the old non dedicated 458 magazine but i didn't. honestly i was so happy it was working, i never looked back. I'll do that this weekend and get an update.
     

    RetiredArmyGuy

    Active Member
    Jan 16, 2018
    171
    Pasadena, MD
    Tangent - does this round need a stronger receiver? I think I read that CMMG uses a beefier lower for their 458.

    It isn’t necessary as the max PSI is around 35k which is fine regarding backthrust and wear on parts. There is no more stress on the upper and lower outer housing than on a 5.56.
     

    Moorvogi

    Firearm Advocate
    Dec 28, 2014
    855
    happy (and surprised) to report there's still no issue w/ the firearm. issues appear to be resolved w/ a good scrubbing of the BCG and a dedicated magazine. i did change to a non-dedicated magazine and issues resumed. You can see SCRAPE marks where the bullet feeds into the chamber.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    That's interesting, if only because there's a lot of guys running 458 SOCOM who claim you don't need dedicated mags. Maybe they're wrong!

    Sent from my ZTE A2017U using Tapatalk
     

    sinensis

    Member
    Sep 4, 2018
    67
    Columbia, MD
    I took my .458 to the range for the first time, using Lancer mags w/ Tromix .458 followers and standard 5.56 followers. Both seem to work equally on mine. I don't have a Tromix barrel/bolt however. (BCA barrel and Expo arms bolt). I did have issues with Magpul P-mags with 5.56 followers (round wouldn't chamber correctly all the time, would need to pull back bolt slightly and release to chamber). I suspected it was because the range was a sit down bench rifle range (Elk Neck State Forest) and the gun was resting on the bottom of the mag, and i guess could of been pushing the mag in at a weird angle.
     

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