Is there a difference between M118LR and 175 Federal GMM?

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  • Qbeam

    Ultimate Member
    Apr 16, 2008
    6,074
    Georgia
    Just a random thought. Is there any real difference between the two?


    Q
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Just a random thought. Is there any real difference between the two?


    Q

    Different powder, brass and primers. Mk316 and FGMM use IMR 4064, M118LR uses RL15 or IMR4895. FGMM is also a hair shorter at 2.805 and fits 308 PMAGs, M118LR is 2.830. All in all similar velocities and accuracy, but not identical.
     
    Last edited:

    Qbeam

    Ultimate Member
    Apr 16, 2008
    6,074
    Georgia
    Thanks, Alucard.


    Is there a difference in performance? I also wonder why the OAL is different.





    Q
     

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Thanks, Alucard.


    Is there a difference in performance? I also wonder why the OAL is different.





    Q

    Ed Shell probably knows all about them, but IIRC M118LR was made primarily for the M24 and other bolt action platforms, and was as long as could be loaded in an M14/MK14 magazine for use in both platforms. It uses crimped mil-spec primers, and is kinda hot, it's harder on M14 actions, spec is 2700+ FPS depending on verision. The newer MK316 is a little lighter load at 2600-2650FPS, and loaded shorter, better for MK11(SR-25) and MK17(FN SCAR), and can fit in their mags easier, it's just basically a mil-spec standard version of FGMM with flash retardant, and better for semi-auto platforms.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    It uses crimped mil-spec primers,

    Are you sure about that?

    I thought that M118LR is not crimped primers.

    I have a box of once fired, but I have not processed it.

    Yeap, not crimped:

    The M118 Special Ball Long Range, more commonly known as M118LR, also went back to utilizing match cases and a press fit, not staked, primer No. 43.

    FYI
    The powder used on the original M118LR was 44 grains of WC 750 and of course the 175gr Sierra Match King bullet is utilized.

    For later ammunition:

    The Federal Cartridge Company was awarded the contract and the ammunition was designated the M118 Special Ball Long Range Mk316 Mod 0. Like with the M118LR, the name was just modified to keep from having to go through full classification for the new ammunition. Federal designed a new match case based on their Gold Medal Match cases and used a modified extruded propellant. Unfortunately the details of which propellant and the charge weight are not widely known at this time. Federal also uses their Gold Medal Match primer for this load. Essentially it is a specialized commercial load adapted for the military specifications. Part of the requirements also included much higher quality control measures which are probably nothing more than what Federal currently does on their commercial Gold Medal Match manufacturing line.

    So it seems that Mk316 is basically the same as FGMM, but the original M118LR is different.
     
    Last edited:

    alucard0822

    For great Justice
    Oct 29, 2007
    17,643
    PA
    Are you sure about that?

    I thought that M118LR is not crimped primers.

    I have a box of once fired, but I have not processed it.

    Yeap, not crimped:



    FYI

    For later ammunition:



    So it seems that Mk316 is basically the same as FGMM, but the original M118LR is difference.

    Good to know, could have sworn they were crimped #43s. Had a bunch of it, and it shot well enough, but FGMM usually shoots better.
     

    454shooter

    LARGE Caliber
    Jun 20, 2020
    71
    Harford County
    Not my words, but good information:

    M118LR has had a few variations during its life - the initial loadings for it in 1995 used WC750 (42.8grs) and was not intended for use in an M14. MV in an M24 ran 2660 (24" bbl)

    From 1996 - 1999, 118LR used 43.8 of WC750 - and this ran 2750 out of an M24. The last lot of that ammo was LC99C173-013. Definitely do not use that in an M14.

    Later in 1999, the recipe changed - the powder was switched from WC750 to REL15. That loading used 44.3grs. MV out of an M24 ran 2750. The impetus for that was improved temperature sensitivity.

    In 2002-2003 the Army & the Marines began using M118LR in their M14's in the desert and as can be expected - there were reports of damaged/broken op rods and other parts from deployed units in Iraq.

    In 2003 & 2004 the load was reduced again - and it varies based on, as Lysander correctly stated, they load to a velocity standard. This load varied between 42.8 - 43.1 of REL15. Velocity ran 2709 from an M24 and 2685 from an M14. Both the Army and the Marines authorized this ammo for use in the M14DMR & M110 rifles. Performance in the M110 was poor due to the loss of velocity (20" bbl).

    Mk316 is another animal altogether. Developed in 2008 as a joint SOCOM/Navy effort with Federal Cartridge Co. That stuff started life with 41.7 of IMR4064 with flash reduction modifications. The brass was specialized for this requirement. It had more uniform neck concentricity and beefed up web/case head area. They use Federal 210M primers.
    Out of an M24, MV runs 2640. It was not intended for use in M14's, but rather the MK11 and the MK17. It should be ok to use with an M14.
    Federal really pulled out the stops for this ammo - each lot is loaded with single lots of primers, cases, bullets and powder - no mixing or blending. Consistency is amazing - (which is what we hand loaders do anyway.)
     

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