Do I need a new cam pin? Which is best?

AR/M4 AR Technical Discussion
1

I think my cam pin is looking pretty sad.

Is the LWRC “improved” cam pin good to go in a DI? I read the other thread about the POF roller pin, and I don’t want it. I’m just looking to get a top quality 1 piece. Here are pics of the madness…

Prepare yourselves, it is a RRA mid length upper with only ~800 rounds through it:eek:. Zero malfunctions so far, and I want to keep it that way. Is this cam pin wearing fast or is it just me? Maybe this is an inferior cam pin? BTW, I wiped all of the oil off of it for this pic. I always keep it heavily lubed with Breakfree LP (not CLP).

Thanks

2

woah, first pic through me off for a sec until i realized what it was. Looks fine to me.

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Wow. I just thought it had lots of wear, but I am new to AR-15’s. So the ledge/groove that goes around it is ok? How do I know when it should be replaced?

I guess it just threw me off because all other parts that show wear are just lightly polished and smooth looking, but this looks all beat up.

Thanks for the advice.

5

lol same here

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cam pins probably dont “wear out,” but they wear enough to cause enough play between the bolt cam-pin hole and the cam pin, which breaks bolts.

cam pin should be replaced somewhere between 3 and 5k, in my opinion.

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I would not run that pin in my gun. You are right about the ledge/grove. Buy from a quality company. A few dollars spent now may save you a lot of money in the long end. Just my 2 cents.

10

Thats a little more wear,particularly on the side of the pin,than I would expect to see with only 800 rounds.Also looks like there is burnishing at the upper and lower surface of the pin post from the bolt,as if the cam pin is loose fit in the bolt and rocking.I’d personally replace it with a LMT or BCM cam pin and run it wet with a good lube…I prefer Weapon Shield CLP and it works.
I also use a small chrome plated screw driver to scribe an arrow(leaves a black arrow) on top of the cam pin to ensure it is installed in the same direction every time.This seems to keep a consistent wear pattern on the cam pin.
Personally for five bucks I replace the cam pin when I feel the need no matter the round count.If it looks unusual I toss the old and in with a new.

11

Wouldnt it be better to replace opposite direction every time to distribute the wear? Like rotating the tires?

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Buy a couple of cam pins from BCM and be done with it. Never hurts to have xtra around for maintenance.

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From what Ive read on the subject here and other places its indicated that the cam pin being installed in the same direction allows the bearing surfaces to retain a consistent wear pattern.In other words the same bearing and impact surfaces stay in contact with each other and matched,rather than one burnished over the other time after time.
I dont think its a critical or really even a necessary procedure to follow,but from what Ive seen since implementation the wear pattern is more consistent and the cam pins seem to retain their fit within the bolt longer.So I do it.
No its not like rotating tires which is done to keep a consistent wear pattern and profile of the surfaces that are run at different angles and forces due to the tires being engaged under different levels of friction and load from steering,stopping and acceleration etc. and run in full rotation of 360 degrees.
The cam pin being fixed into position as its cycled within its track which dictates the same friction and impact areas as it does not rotate 360 degrees as its cycled.So there are basically friction wear surfaces on the sides and impact surface on the front,with each a bit different than the other due to the machined surfaces within the cam pin track of the carrier.When reversed the surfaces are burnished in an opposite direction again changing the pattern and increasing wear as material is displaced.
Then you have the lower part of the cam pin that engages the bolt which can have its own wear patter due to the machined port of the bolt and being fixed into position.
Thats my thinking on it and it may be flawed as Im not an engineer,but that how I see it.