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Discussion Starter · #1 ·
When cleaning my MR556 today I noticed some wear in the upper from the cam pin that I never did before. I put around 500 rounds through it before having my barrel reprofiled and getting a suppressor.

This is my first time cleaning it since shooting it suppressed. I know HK added relief cuts I'm this area, but it doesn't seem to be helping. I also know increased wear is expected, but is this normal after only shooting around 300 rounds suppressed?

Can anyone else post picks of suppressed and unsuppressed MR556s/416s for me to compare?












 

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Ive switched all my hk/ar pins with the cam roller pin from patriot ordnance factroy (pof), to keep from excessive wear, but ive never found it like that bad before i made switch
 

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Discussion Starter · #5 ·
Ive switched all my hk/ar pins with the cam roller pin from patriot ordnance factroy (pof), to keep from excessive wear, but ive never found it like that bad before i made switch
Can you post some pictures? Where did you pick up the roller cam pin?
 

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Ive switched all my hk/ar pins with the cam roller pin from patriot ordnance factroy (pof), to keep from excessive wear, but ive never found it like that bad before i made switch
hey :) do you think the POF Roller Cam Pin (.308/7.62) will fit the MR308/MR762? How's the fitment in the mr556? Does it work well?

best regards
 

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Ive switched all my hk/ar pins with the cam roller pin from patriot ordnance factroy (pof), to keep from excessive wear, but ive never found it like that bad before i made switch
I was going to ask if it was possible to do that switch. That's what I'll do too then.

The wear is completely normal!!
Well, after 1000 rounds, I wouldn't call that "normal" ...
 

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I too, use the POF roller cams. Great idea taken from the M14.

Here's a little test to tell you just how the wear dynamics effect an AR series rifle..... First, completely clean an AR type rifle to bear metal, no lube at all. Then, with the upper removed, slide the BCG in and out of the upper to get a feel of how it works with no resistance.... Then, without placing the bolt into battery, use a finger to apply pressure on the front of the bolt with the BCG a couple of inches out of battery to mimic the bolt coming into contact with the rounds in the magazine. You'll notice that the BCG tips to the right (OPV Operators Point of View) and moving the bolt is more difficult then just overcoming the force you're placing on the bolt face. Then place a log of bolt face while pushing forward on the rear of the BCG and you'll feel the entire BCG lock up. You can even lift up the entire upper (barrel facing down) without the BCG coming out of the upper if you place enough opposite force on the bolt face and the rear of the carrier.

This is because of the force on the cam pin being pushed to the left into the side of the receiver before it enters the cam pin cut out which would allow the bolt to rotate and go fully into battery. This could be what causes that wear just before the cam pin cutout. Especially after the round is stripped from the magazine and enters the chamber. That's when the extractor hits the rim of the cartridge and has to snap up and over that rim. At this point, the carrier is about a full 3/8" out of battery, locating the cam pin very close to the rear edge of the cam relief.

This could be where the most force is applied to the bolt and causes that wear just on the edge of the cam pin cutout as that is the last part of the cycle before the BCG is far enough forward to fully rotate into battery. The stronger the extractor spring and/or "O" ring, the harder it is for the extractor to overcome the lip of the cartridge and the more force is transferred back to the cam pin on the receiver. Fortunately these forces are placed on the locking lugs and BCG at this point so it really shouldn't be an issue unless there is something else at play.

Steel on aluminum isn't the best idea normally, but the forces are not great enough to cause enough damage to cause a malfunction unless the gun is extremely dirty, under-lubed (or not at all) or has a lot of particulates in it like sand and whatnot.

I'm surprised the original design (AR15/M16) didn't come with a roller cam to begin with.

Of course it will always work better lubed as it's supposed to be because it's a mechanical tool and anything mechanical always works better with lube.

Point being, removing as much friction as possible with the roller cam is a good thing.
 

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I was going to ask if it was possible to do that switch. That's what I'll do too then.


Well, after 1000 rounds, I wouldn't call that "normal" ...

Once again, say what you will, you asked if it was "normal wear for the platform".. I have seen Hundrreds and they all have that same exact wear!! Would you like to see my SIG MPX after only 100rds??

I too run the POF Roller cam pins in my AR uppers and now I think Lantac makes a rounded top roller cam pin with no moving parts.

The never 416 and MR556 uppers have the corner milled off to minimize the amount of wear.


Yes, it is NORMAL..
 

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When cleaning my MR556 today I noticed some wear in the upper from the cam pin that I never did before. I put around 500 rounds through it before having my barrel reprofiled and getting a suppressor.

This is my first time cleaning it since shooting it suppressed. I know HK added relief cuts I'm this area, but it doesn't seem to be helping. I also know increased wear is expected, but is this normal after only shooting around 300 rounds suppressed?

Can anyone else post picks of suppressed and unsuppressed MR556s/416s for me to compare?












This is actually minimal wear as it has the newer milled upper..
 

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Ive switched all my hk/ar pins with the cam roller pin from patriot ordnance factroy (pof), to keep from excessive wear, but ive never found it like that bad before i made switch
I've got 5 AR's including my MR and I replaced 'em all . I have a POF 308 and that's where I saw the benefit. I've got about 400 rds on my 308 and the corner looks new .
 

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i first seen these at the NRA convention at L'ville at the POF display, already had several of their rifles and having a MR i bought enough pins to do all mine ar platform rifles, wouldn't have it any other way
 

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The new Lantac design is nice as it has no moving parts!! I have always been concerned of the POF cam breaking causing a Catastrophic Malfunction seizing the BCG.. HOWEVER, I have never read or heard of one doing so!!
 

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Also looks like someone posted screen name jjackson2491 headline Mr556 question, anything to worry about? I don't see a resolution to his post back 2013.
 
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