[Willard]

I would suggest a picture with the upper removed along with the bolt, from the bottom up.
Also a picture of this "roller cam pin". I'm not familiar with this improvement, and wonder aloud, if it would require a special upper receiver or not.

My gut reaction is why is it needed... the cam pins function is to connect the bolt to the carrier. It has a "rectangular" head to allow insertion into the bolt and carrier, and once in rotated 90 degrees to allow the firing pin to pass through, and with it turned 90 degrees, it cannot come out, even if the firing pin breaks in half because of the "rectangular" top.

If someone can explain what the purpose of the "roller" is, maybe I can understand its improved function.

 

[xrlizard]

Here is a pic of the wear from my cam pin.

I do not know what is considered normal on this, other than wear in the area is common and generally not considered a significant issue. I still did not care for the wear, so I swapped it out for a POF roller after maybe 700-800 rds through it, and I can't remember if it had this much wear before the roller cam or not, but I will say, I cannot see any wear marks on the roller pin itself, so it may have already worn as much as it was going to, prior to my installing the roller. I added some grease to the channel, to see if there was contact, and it did spread the grease a bit, when I manually slid the bgc and handle back and forth a few times. I tried just moving the bcg, and could still see it was making contact with the grease and spreading it a little beyond the wear marks. Not definite proof, but may indicate it is making some contact, and not increasing the wear.

It is not obvious from the pic, but the wear is 1mm deep or less. It has two other small wear spots in the finish near the cam pin wear, but they do not cut into the upper like the cam pin wear, and just look like rubs in the finish of the channel.

Regarding why is the roller cam needed, there seems to be a good deal of debate as to whether they are beneficial or not. Proponents say they reduce wear and smooth out the action a bit. Opponents say they don't do anything at all and could be a potential source of breakage, since they introduce a mechanical roller piece into the action. From what I read on cam pin wear, it is common, normally happens when the gun is new, and after it wears in to a certain point, should stop increasing.

I decided to try the roller pin out, since they are pretty cheap and I really haven't heard of any problems being caused by them, but as I said, I cannot remember if this wear pattern is the same as before I added it, and I cannot tell any difference in the smoothness of the action, but mine has always seemed pretty smooth anyway. If you are really interested in checking into the wear issue, another way to test if it stops at some point, would be to get a new regular cam pin, install it and see if you are getting wear on the new pin's finish.

 

[Steve40th]

I guess we shall see when I get permission to run my 300BLK SBR, as it will have one. I know it DI, but it will be new, with the roller.
I am under the impression piston AR's benefit the most from this roller pin.