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Thread: MK 248 MOD 1

  1. #1
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    MK 248 MOD 1

    Has anyone loaded their own 300 Win mag to the mk 248 mod 1 specs? And, what is the brass life that you have encountered?


    jpgm

  2. #2
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    A guy I shoot with tried it in two rifles. In a factory Savage it was definitely too hot and the brass was toast (Lapua). In his Remington with a custom Bartlein barrel it was also to0 hot, but the brass was reloaded 1X, I do not think he will get more than 2x reloads out of them.

    That particular load of H1000 is way too much in my opinion, brass life will be the least of your concern. That load is kind of a beast, QL puts it at like 70K PSI under perfect conditions.

  3. #3
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    Quote Originally Posted by eightmillimeter View Post
    A guy I shoot with tried it in two rifles. In a factory Savage it was definitely too hot and the brass was toast (Lapua). In his Remington with a custom Bartlein barrel it was also to0 hot, but the brass was reloaded 1X, I do not think he will get more than 2x reloads out of them.

    That particular load of H1000 is way too much in my opinion, brass life will be the least of your concern. That load is kind of a beast, QL puts it at like 70K PSI under perfect conditions.
    This begs the question of what do these two civilian rifles actual chambers look like, specifically the throat length, diameter and angle.

    You can see below why the chamber pressures are higher.





    As a side note the SAAMI interchangeability warning for .223/5.56 ammunition did not come out until 1979 when the military introduced M855 ammunition that required a longer throat. I'm saying this because my Savage .223 has a longer throat than my two AR15 rifles do.
    Last edited by bigedp51; 10-09-13 at 16:57.

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    Quote Originally Posted by bigedp51 View Post
    This begs the question of what do these two civilian rifles actual chambers look like, specifically the throat length, diameter and angle.

    You can see below why the chamber pressures are higher.





    As a side note the SAAMI interchangeability warning for .223/5.56 ammunition did not come out until 1979 when the military introduced M855 ammunition that required a longer throat. I'm saying this because my Savage .223 has a longer throat than my two AR15 rifles do.
    First thing to remember in this case is that there is no "mil spec" for the .300 Win Mag, Black Hills was simply given the task of loading ammo to a certain desired spec that would not blow up a loose throated military gun on a hot day. The 248-1 load is 70K PSI under nominal conditions in mil barrels, and thusly, should not shock people when its too hot for your average 300 mag.

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    Quote Originally Posted by eightmillimeter View Post
    First thing to remember in this case is that there is no "mil spec" for the .300 Win Mag, Black Hills was simply given the task of loading ammo to a certain desired spec that would not blow up a loose throated military gun on a hot day. The 248-1 load is 70K PSI under nominal conditions in mil barrels, and thusly, should not shock people when its too hot for your average 300 mag.
    If it is shot by the military it has mil-spec requirements and Black Hills was awarded the contract to manufacture this "mil-spec" ammunition after reviewing all the bids made by the other manufactures.

    http://usarmorment.com/pdf/300WM_load%20data.pdf

    http://www.dtic.mil/ndia/2009infantr...ioniii8524.pdf

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    I had the original load and components data somewhere. The powder is H1000 and the bullet is the 220 grain Sierra Match King. It is loaded longer than the SAAMI maximum cartridge length. I think it is or was 3.5 inches. It might be 3.45" or somewhere around there but the original length was suppose to be 3.5 inches.

  7. #7
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    I have about 20 cases from M248 mod 1 that was shot by an acquaintance through a rifle that was set up for it during a range outing a while back. About 75% have some degree of gas leakage around the primers. It's too doggone hot. I understand why they went with the projo they did and loaded it to the level they did, but I have to think that SOMETHING with a better BC could have given them the degree of forgiveness and transition they were looking for at a lower pressure.
    Duane Liptak, Jr.
    Director of Product Management and Marketing, Magpul Industries
    Director of Magpul Dynamics

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