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Posted: 7/25/2025 10:36:22 PM EDT
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Any possible issues using a Roller Cam Pin on SUP ARMS Piston set-up? Have a few of these pins in stock and I can't think of any but thought I would check with the Experts on Piston Systems. Thanks for your time. |
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Bought one about a year ago, but after eye balling it, thought the little tit that holds the roller on the end looked like the most likely thing to break, so I tossed it in the box where stuff goes to be forgotten. But seeing others are having good luck, I may dig it out some day, and give it a try. |
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Shit idea. Will start hammering a divot in the cam pin track where the pin is contacting the inside of the upper when the bolt impacts the rear of the top round in the magazine. It's about surface area. A flat cam pin spreads the impact on a flat surface, the roller reduces that impact to the specific spot the roller is contacting. If you always have the luxury of a super clean gun with lots of lube, it will work for awhile. Get the gun dirty, run suppressed, and run it for more than a couple mags at a time and the system has to overcom more fouling and the stresses increase wear on the components. I used to run a roller cam in a 416 and the divot formed and caused hard cycling. Easy to feel when hand cycling a round off the top of the magazine. Of course the strength of the 416 action spring overcame the roughness, but the divot formed in the cam pin track was just no bueno for me. That and i've never had an issue with a standard cam pin that a roller pin actually solved. In other words, it's snake oil and can lead to potential damage to the anodizing and underlying aluminum. Solution in search of a problem. |
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Originally Posted By LeviBarAlphaeus: Shit idea. Will start hammering a divot in the cam pin track where the pin is contacting the inside of the upper when the bolt impacts the rear of the top round in the magazine. It's about surface area. A flat cam pin spreads the impact on a flat surface, the roller reduces that impact to the specific spot the roller is contacting. If you always have the luxury of a super clean gun with lots of lube, it will work for awhile. Get the gun dirty, run suppressed, and run it for more than a couple mags at a time and the system has to overcom more fouling and the stresses increase wear on the components. I used to run a roller cam in a 416 and the divot formed and caused hard cycling. Easy to feel when hand cycling a round off the top of the magazine. Of course the strength of the 416 action spring overcame the roughness, but the divot formed in the cam pin track was just no bueno for me. That and i've never had an issue with a standard cam pin that a roller pin actually solved. In other words, it's snake oil and can lead to potential damage to the anodizing and underlying aluminum. Solution in search of a problem. We're all waiting for the proof you undoubtedtely have. Not snake oil; way less force to unlock the bolt. It's usually one gas setting's worth of difference with an SA piston kit. |
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Originally Posted By lew: We're all waiting for the proof you undoubtedtely have. Not snake oil; way less force to unlock the bolt. It's usually one gas setting's worth of difference with an SA piston kit. The head/roller part of the cam pin has exactly zero to do with the unlock phase of the cycle of function as the cam pin head is literally free-floating in the cam pin recess of the upper receiver during the firing/unlocking, and beginning of the extraction phases of the cycle of function. The roller would only have benefit during the loading phase when the head of the cam is riding on the inside of the receiver, and especially after the bolt makes contact with the top round of the magazine when the most force is applied rearward on the bolt due to the friction of removing the round from the magazine. The coating would be responsible for smoother unlocking. An NP3, NiB, DLC, etc. coated standard cam pin would likely produce the same results. Learn the system before dunning-krugering yourself in public. |
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