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.
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?
