HK MR762 Malfunctioning
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Thread: HK MR762 Malfunctioning

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    Default HK MR762 Malfunctioning

    I purchased an MR762 earlier this year. I’ve shot only federal gold medal match 168 grain ammo through it with two different 20 round magazines. The gun commonly short strokes and jams. I’ve tried cleaning it the best I can and lubricate it according to the manual. I sent the rifle to HK and they increased the gas port size and replaced the gas block and shot 168 grain federal gold medal match (20 rounds I believe).
    They said the fired from the hip and the shoulder and it works. Every time I have fired it it I fire it from the shoulder. It seems to work well for the first magazine or so and then starts having issues. I’ve only bought one batch of the ammo and gone through a couple hundred rounds. I called today to see what HK thought and they said they really are unsure of what to do and they told me that the federal gold medal ammo is weak and that I should use hotter ammo. I’d like to use that ammo for its accuracy but does anyone have any recommendations? Do you think different ammo would help? If so what kind? Maybe I got a bad batch/case of 500 rounds? I love the rifle for when it works but it’s been disappointing because it has actually been one of the least reliable guns I have ever owned based off my experience to this point.

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    I would try some NATO 7.62 and see what happens, I don't think for a minute Fed. GMM is weak ammo but could be yours needs a little break in more than some.
    When I had mine it choked on the first round PRVI Match ammo but ran fine with GMM.
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    All new rifles need a wearing-in period to get things smoothed up. As mentioned, I'd run a bunch of good NATO through it.

    All part of the fun of having them.

    DG
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    Please keep us updated with your results, thanks.

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    Quote Originally Posted by Kisara View Post
    Please keep us updated with your results, thanks.
    I'll keep coming back when I feel like I have more information but I did take it to the range a few days ago and have this to share. Granted I only shot about 25 rounds out of it but had no malfunctions with it. I shot two other types of ammo, one was a full box of aguila 7.62x51 ammo and the other was 5 rounds of winchester. Other things I did differently was this time I applied grease instead of oil/clp to the internals, except I applied a pretty healthy amount of oil to the recoil spring/buffer. My thoughts were that HK claimed good success of the rifle in their factory but I had only sent the upper so maybe my issue is more related to the recoil spring/buffer? I kept pulling the charging handle all the way to the rear and letting go probably about 100 times. I actually started to smell like a burning smell and noticed it was grinding/smoothing out something as a very fine dust was starting to pop up right by the charging handle. I took some advice I read on here from previous posts and locked the bolt back for a day. I tried to see if all of these things maybe would help to loosen up the spring a little bit. Overall I had good success doing this but it was also a low round count and maybe it was luck maybe there was something to it? If it is working as it should now I'm not sure which of these necessarily was the cause or if it could be a combination. Again I'll give updates later on bu it also might not be for a few weeks/months depending on when I take the rifle out again.

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    Quote Originally Posted by Anglefan View Post
    I'll keep coming back when I feel like I have more information but I did take it to the range a few days ago and have this to share. Granted I only shot about 25 rounds out of it but had no malfunctions with it. I shot two other types of ammo, one was a full box of aguila 7.62x51 ammo and the other was 5 rounds of winchester. Other things I did differently was this time I applied grease instead of oil/clp to the internals, except I applied a pretty healthy amount of oil to the recoil spring/buffer. My thoughts were that HK claimed good success of the rifle in their factory but I had only sent the upper so maybe my issue is more related to the recoil spring/buffer? I kept pulling the charging handle all the way to the rear and letting go probably about 100 times. I actually started to smell like a burning smell and noticed it was grinding/smoothing out something as a very fine dust was starting to pop up right by the charging handle. I took some advice I read on here from previous posts and locked the bolt back for a day. I tried to see if all of these things maybe would help to loosen up the spring a little bit. Overall I had good success doing this but it was also a low round count and maybe it was luck maybe there was something to it? If it is working as it should now I'm not sure which of these necessarily was the cause or if it could be a combination. Again I'll give updates later on bu it also might not be for a few weeks/months depending on when I take the rifle out again.
    I wandering if the fine dust was tungsten from the buffer. Maybe your buffer was/is leaking tungsten.
    "Just because you're paranoid doesn’t mean they're not after you!"

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    Quote Originally Posted by RegularGuy461969 View Post
    I wandering if the fine dust was tungsten from the buffer. Maybe your buffer was/is leaking tungsten.
    When I take it apart I'll see if I can notice any wear on the buffer. Would it be leaking or getting worn? Is it any concern or any fix you'd recommend if it turns out to be the case?

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    Quote Originally Posted by Anglefan View Post
    Quote Originally Posted by RegularGuy461969 View Post
    I wandering if the fine dust was tungsten from the buffer. Maybe your buffer was/is leaking tungsten.
    When I take it apart I'll see if I can notice any wear on the buffer. Would it be leaking or getting worn? Is it any concern or any fix you'd recommend if it turns out to be the case?
    Unless buffer is cracked I don’t see how the tungsten could be coming out.

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    Measure the GMM with a caliper. They should all be very close to being the same . If not well there is your problem.
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