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Thread: LMT MRP piston Cam Pin Wear? - Pics

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    LMT MRP piston Cam Pin Wear? - Pics

    i wanted you guys to take a look at my firing pin and tell me if this was a known problem w/ piston ar15s? Mine is the LMT piston if you didn't know and I've fired roughly around 800rnds? Here are some pictures of my firing pin, it looks really gashed, everything else on my bcg looks normal (from what I can tell) I'm still new to this rifle platform.

    Should I just switch my LMT to DI once I get money? What will I need in order to do that for the mrp system? can I just buy a normal DI barrel and install that and will it work with the BCG I already have in my gun? Or do I have to buy a new BCG along w/ that barrel? Thanks for your help



    Last edited by TOrrock; 09-18-10 at 09:51.

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    That is not a firing pin. That is a cam pin.

    Wear in that area is normal. If the wear is beyond surface wear, and there is actually material missing, or a burr forming, then there may be an issue. If so, I would suspect your BCG cycle speed is too high, meaning the BCG is getting hammered more than it needs to be. Is there a way too adjust your gas piston system ( like: suppressed - unsuppressed)? Are you running a suppressor?
    Last edited by Jimbo45; 09-18-10 at 04:19.

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    Quote Originally Posted by Jimbo45 View Post


    That is not a firing pin. That is a cam pin.

    Wear in that area is normal. If the wear is beyond surface wear, and there is actually material missing, or a burr forming, then there may be an issue. If so, I would suspect your BCG cycle speed is too high, meaning the BCG is getting hammered more than it needs to be. Is there a way too adjust your gas piston system ( like: suppressed - unsuppressed)? Are you running a suppressor?
    no suppressor, everything is stock LMT. I don't know of any adjustment thing. There's the piston rod and top piece, but there doesn't seem to be anything to adjust.

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    What receiver extension, spring, and buffer are you using?

    Maybe you have a soft cam pin?

    It is hard to tell exactly, to what extent the cam pin is worn/damaged, to determine if it is normal wear or not. If there is actually excessive gouging, I would contact LMT, if it were me.
    Last edited by Jimbo45; 09-18-10 at 06:26.

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    Quote Originally Posted by Jimbo45 View Post
    What receiver extension, spring, and buffer are you using?

    Maybe you have a soft cam pin?

    It is hard to tell exactly, to what extent the cam pin is worn/damaged, to determine if it is normal wear or not. If there is actually excessive gouging, I would contact LMT, if it were me.
    Like I said everything is stock that came w/ the LMT MRP except the stock which is a CRT magpul mil spec stock, but I just change that recently

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    Quote Originally Posted by rifle_eyes View Post
    Like I said everything is stock that came w/ the LMT MRP except the stock which is a CRT magpul mil spec stock, but I just change that recently
    I was reading fast, and missed the MRP part before making my first post, so I guess you wouldn't have any adjustment options. I never saw where you mentioned it was a complete factory rifle, as opposed to a piston upper, placed on your lower.

    So, are the marks I see finish wear, or actual divots in the metal?

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    Not being sure how your bolt is set up.

    By removing the gas rings on your bolt and replacing with a bolt spring is suppose to help/stop cam pin wear.



    good luck

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    I just installed an LMT enhanced bolt carrier in my 6920 along with a new cam pin, bolt, and firing pin. I shot about 300 rounds through it and my cam pin has the same wear marks as yours.

    I compared to my original cam pin and the wear is definitely more profound on the new parts. I compared the cam pin tunnels on the two bolt carriers and I think the cause is due to a combination of LMT's tunnel configuration and the freshly machined edges. I think that as I put more rounds through it the machined edges will smooth out and then I will throw in a new cam pin.

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    Quote Originally Posted by EzGoingKev View Post
    I just installed an LMT enhanced bolt carrier in my 6920 along with a new cam pin, bolt, and firing pin. I shot about 300 rounds through it and my cam pin has the same wear marks as yours.

    I compared to my original cam pin and the wear is definitely more profound on the new parts. I compared the cam pin tunnels on the two bolt carriers and I think the cause is due to a combination of LMT's tunnel configuration and the freshly machined edges. I think that as I put more rounds through it the machined edges will smooth out and then I will throw in a new cam pin.
    so you're saying just keep wearing the gun out more? like I haven't had any malfunctions out of any of my shots all of them that i've shot, but the wear worried me, they look pretty deep, but i dunno. you can barely tell by moving your thumb over them, but def some difference in surface. I contacted LMT and they told me it was normal wear and all the piston rifles did that, which didn't really make sense. does this mean that I'm going to have to replace parts on it all the time just because it's a piston rifle? I bought the rifle on impulse not knowing much about the ar15 platform, mostly just shooting 10/22s and my glock 19, but the local gun dealer that I went to which is Clyde armory (https://policeguns.com/catalog/) he sold me into the piston mentioning how it had the same function as the ak47, so basically the same reliability, plus my BCG would be a lot cleaner and cooler & all of this sounded wonderful to me being a noob, not realizing it seems like a gimmick and is only eating away at my rifle, which I spent a little more on because I wanted a solid AR rifle that would last and had a reputation.

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    Quote Originally Posted by Frank207 View Post
    Not being sure how your bolt is set up.

    By removing the gas rings on your bolt and replacing with a bolt spring is suppose to help/stop cam pin wear.



    good luck
    I don't have one of those on mine, where did you get that bolt spring and can I use that on an LMT? I read somewhere on their site that they only use LMT barrels and stuff because of the way their MRP is set up which is kind of a bummer because it limits the customization options and I can only use LMT barrels/bolts and stuff, but I guess on the other side everything they make should be quality.
    Last edited by rifle_eyes; 09-18-10 at 09:42.

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