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Thread: Cam-pin wear as a contributor to bolt failure?

  1. #21
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    Quote Originally Posted by RMiller View Post
    Ya I know.

    My other profession is automotive. Since my work and "gun area" share the same space in my home, I figured why use more products than I have to. Grease and motor oil have been working very well for me. It's crazy smooth when I rack my carbine.

    Besides a dedicated tube of Lucas red and tacky and a qt of royal purple SAE 30 will last forever! And I can use it on my truck in a pinch. What's not to like?
    Yeah, same deal, only with the addition of 20W50 Lucas for out ludicrously balls-hot days if I need something that kinda does both.
    عندما تصبح الأسلحة محظورة, قد يملكون حظرون عندهم فقط
    کله چی سلاح منع شوی دی، یوازي غلوونکۍ یی به درلود
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  2. #22
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    cam pin wear

    notice the wear on a brand new BCM BCG after about 500 rnds, just been rotating it after everytime i shoot a match. does seem to have spread the wear out. but if anybody wants a cam pin will trade for 40 lbs of H322I've been using EWL 30 weight, really like the fact that it stays in place on hot day's(90+) and does'nt gum up in the cold(-15 with wind chill)

  3. #23
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    Quote Originally Posted by MK18Pilot View Post
    I think you'll find that cam pin lash is the primary cause of the wear. The TDP spec for the cam pin diameter and the hole in the bolt are nearly the same. To speed production and reduce returns, most manufacturers make the hole in the bolt to big and the pin to small.

    When the pin is too small and the hole to large, the unlocking force isn't lateral to rotation of the bolt and the pin rocks in the bolt hole. This leads to impact between the carrier and cam pin.

    I'm not sure if the ledge that is created is a result of loss of material due to wear or if the carrier is "hammer forging" the area of cam pin that contacts the carrier to a smaller dimension.
    I think this is the biggest culprit right here. Loose fitting pins.
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  4. #24
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    Quote Originally Posted by Clint View Post
    I think this is the biggest culprit right here. Loose fitting pins.
    My Daniel Defense BCG cam-pin was 0.001" or so (I forget, but there was a spec difference when I mic'ed it, extremely small difference) larger than the RCA cam-pin, and I could feel with my hands slightly more movement in the RCA setup, yet it delivered less wear, which is to say, no wear vs. catching my fingernail.
    Last edited by WS6; 07-04-13 at 00:32.

  5. #25
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    Okay, I'm finding tons of good info about the cam pin along with pics using the search button.

  6. #26
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    I use an NiB cam pin in my LMT E-carrier and LMT std bolt. Some finish wear at the 3,700 round mark but no gouging yet. Nothing catches on my finger nail. I can't remember if I snagged it at Spikes (They're local to me) or if it's an LWRCi. I suspect it's Spikes.

    The cam pin always fit virgin-tight in my LMT bolt. When I first got the pin, it wouldn't go in the bolt without grease using finger pressure alone. Greased and it slid in...haven't really thought about it since.

    I dunno if I would go with HC since it has been more abrasive in texture in my experience.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

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  7. #27
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    This thread needs a gnarly cam pin pic...

  8. #28
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    Quote Originally Posted by patrick sweeney View Post
    My bet is that the cam pin has been swaged, and that once the surface area moved increases to support the load, the metal movement stops.

    I also don't see it as a problem. The carrier is harder than sin, it won't swage/change. the cam pin swages until it supports the load, then metal movement stops.

    I toss such-ridged cam pins when they too bad simply because cam pins are cheap, and I can.

    The tolerance stop is more likely a cause of bolt breakage, and the cam pin wear is just a symptom.
    I agree Patrick. I don't have many of them but I do find that cam pins that are nickel-boron'd or hard chrome typically last 3-4 times longer. I'd like to pick up one of those RCA (Rubber City Armory) BCGs to see how having a nitrided bolt, carrier, cam pin and firing pin all hold up together.
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  9. #29
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    On my BCM BCG the cam pin measures .3105". The bore in the bolt measures .312 on the insertion side.

  10. #30
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    Quote Originally Posted by Tzed250 View Post
    On my BCM BCG the cam pin measures .3105". The bore in the bolt measures .312 on the insertion side.
    My RCA cam-pin measures 0.310. I did not measure the hole in the bolt because I don't trust my calipers and skill to correctly measure it to that close of a tolerance.

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